Pull to Ground
The ECU turns a device on by completing the ground side of the circuit. Also called low-side output or ground trigger.
Trap: The wire may show 12V when off and near 0V when on.
Glossary →Living EFI field guide prototype
Forum advice is not enough. Beginners need the lingo, the User Interface (UI) location, and the correct order.
EFI Triage turns confusing tuning language into plain-English cards, diagnostic branches, ECU-specific UI maps, and safe next steps.
Forum Wizard: “Pull fuel. Check dead time. Verify base timing.”
😵💫
Triage Foreman: “Slow down. What has been verified?”
Start here
The screen is not the engine.
The ECU only knows what the sensors, wiring, calibration, firmware, and software project tell it. A number on the laptop can be an engine problem, a wiring problem, a calibration problem, a dashboard-channel problem, or a process-order problem.
First principle: Verify reality before changing the tune.
Order of operations
- Back up the tune/project.
- Confirm ECU power during key-on and crank.
- Verify TPS, MAP, CLT, MAT, wideband.
- Enter injector data and fuel pressure assumptions.
- Verify base timing with a timing light.
- First start, warm idle, first drive, then boost.
Choose your pace
Idle, Cruise, Throttle Stab, or WOT.
These modes define how much explanation the guide gives you. Early users can read everything in Idle Mode, while experienced users can move faster through checklists, UI paths, log channels, and hard-stop warnings.
Idle Mode — explain it all
For brand-new users. Shows plain-language definitions, glossary links, warnings, diagrams, prerequisite checks, and full procedures before telling you what to change.
Cruise Mode — guided checklist
For users who know some basics but still want structure. Shows the order of operations, UI paths, log channels, normal ranges, and common traps.
Throttle Stab Mode — fast triage
For experienced users moving quickly. Shows the short checklist, pass/fail checks, hard stops, next links, and what not to tune yet.
WOT Mode — pro reference
Minimal hand-holding. Shows direct links to cards, log channels, related procedures, source notes, and advanced caveats. Safety gates still stay visible.
Cards
Short lessons that branch into procedures.
Cards will expand over time. They are the short explanations behind the guide. As EFI Triage grows, new cards will be grouped by electrical basics, sensors, fuel, ignition, software/UI, boost, datalogging, support electronics, and shop talk. New cards can be added without changing the learning path.
5V Reference
A clean ECU-supplied 5V feed for sensors like TPS, MAP, fuel pressure, and oil pressure.
Trap: One shorted sensor can drag down the whole 5V network.
Test procedure →Sensor Ground
The ECU’s clean reference ground for sensor signals. Do not casually treat it like dirty chassis ground.
Trap: Fan or alternator load can make bad grounds look like sensor drift.
Ground branch →TPS
Throttle position sensor. Used for idle state, accel enrichment, flood clear, and driver intent.
Trap: Do not tune accel enrichment before TPS and TPSdot are verified.
Calibrate TPS →MAP
Manifold absolute pressure. The main load signal for speed-density tuning.
Trap: Key-on engine-off MAP should match local barometric pressure, not necessarily sea-level 101 kPa.
Verify MAP →Injector Dead Time
The delay between commanding an injector open and actual fuel flow. Critical at idle and low pulse width.
Trap: Do not hide wrong dead time by mangling the VE table.
Glossary →Base Timing
Commanded timing must match crank timing. Use fixed timing mode and a timing light.
Rule: If the light disagrees with the laptop, believe the light.
Verify timing →Throttle Stab
A quick snap of the throttle pedal. Useful for observing transient response, not steady-state VE.
Trap: A lean spike during a stab does not automatically mean “change the VE table.”
Lean on stab branch →Pull Fuel
Reduce commanded fuel in the active control area. First determine what is actually active.
Question: VE, target lambda, trim, warmup, AE, or fuel pressure?
Decoder →Universal Trip-Up Library
Common problems that look like tuning problems.
EFI Triage tracks recurring garage-level traps across different cars, ECUs, tuning software, and support electronics. These checks are not glamorous, but they prevent people from tuning around mechanical, electrical, or signal problems.
Connector truth
A sensor cannot tell the truth through a bad connector.
- Connector fully seated
- Correct orientation
- Lock tab engaged
- No bent pins
- No pushed-out terminals
- No corrosion or loose terminals
Ground truth
A bad ground can make good parts look bad.
- Clean attachment points
- Tight hardware
- Good engine/body grounds
- Sensor ground kept clean where required
- Voltage-drop tested under load
Power truth
Unstable power creates fake tuning problems.
- Battery terminals clean and tight
- Side-post bolts not loose or stripped
- No hidden corrosion
- No bad stacked accessory leads
- ECU power stable during crank and run
Physical movement truth
The software cannot fix a pedal, cable, or throttle body that does not move correctly.
- No floormat or carpet interference
- Pedal moves freely
- Throttle cable not kinked or frayed
- Throttle body moves freely by hand
- Clips, brackets, linkage, and return spring secure
EFI Triage rule: Before blaming the tune, prove the connection, ground, power, and physical movement.
Triage trees
Start from the symptom. Follow the dependency chain.
Before following a symptom branch, check the Universal Trip-Up Library. Many “tuning problems” start with connectors, grounds, power, or physical movement issues.
Lean on throttle stab
- TPS calibrated?
- TPSdot clean?
- MAP response believable?
- Wideband scaling verified?
- Warm steady-state VE close?
- Then tune accel enrichment.
Starts then dies
- ECU stays powered?
- RPM/sync stable?
- Fuel pressure correct?
- MAP believable?
- After-start enrichment active?
- Idle air configured?
DDefi disagrees with TunerStudio
- Is TunerStudio value correct?
- Is DDefi reading the correct channel?
- Is scaling identical?
- Is CAN/serial data live?
- Compare dash, laptop, and log together.
Procedures
Garage-ready steps.
Procedures are most useful when they are done in the right order. For the ECUGN / TunerStudio startup sequence, start with the Phase One Index and work top-down unless the earlier checks are already verified.
Calibrate TPS — TunerStudio / ECUGN
Fast Triage: Key on, engine off → Tools → Calibrate TPS → capture closed → capture WOT → sweep slowly → verify TPS and TPSdot in log.
Do first: Back up tune, verify throttle linkage, verify 5V reference and sensor ground if readings drift.
Pass: stable closed value, smooth sweep, no dropouts, returns to closed, WOT reaches expected full range.
Do not touch yet: Accel enrichment.
Verify Wideband Scaling
Fast Triage: Confirm controller model → match 0–5V curve in ECU → compare gauge vs TunerStudio/log → verify lambda/AFR display convention.
Trap: The wideband gauge can be right while the ECU is wrong.
Watch: AFR/lambda, target, EGO correction, battery voltage, fuel type/stoich assumptions.
Verify Base Timing
Fast Triage: Lock/fix timing → command known value → use timing light → adjust trigger offset if needed → recheck → return to normal timing mode.
Hard stop: Do not tune ignition or boost if commanded timing does not match crank timing.
ECU and support electronics
Choose your ECM. Choose your support electronics.
This prototype starts with ECUGN/TunerStudio and DDefi because that stack has real beginner friction: software project layers, channel mapping, dash interpretation, and TunerStudio UI navigation.
Start with the Phase One Index for ECUGN / TunerStudio setup order. If values disagree between the ECU, dash, logger, or gauge, check the Universal Trip-Up Library before blaming the tune.
Recommended path: ECUGN/TunerStudio + DDefi Dash → verify TunerStudio value first, then map dash channel/scaling.
Glossary + Shop Talk Decoder
Plain meanings with related branches.
Glossary terms explain the language. The Universal Trip-Up Library explains the common real-world problems behind the language. For ECUGN / TunerStudio setup order, use the Phase One Index.
TPS — Throttle Position Sensor
Throttle Position Sensor. TPS tells the ECU what your foot is doing. It is used for idle state, accel enrichment, flood clear, throttle movement rate, and driver intent.
MAP — Manifold Absolute Pressure
Manifold Absolute Pressure. MAP tells the ECU engine load by measuring absolute pressure in the intake manifold. Key-on engine-off MAP should be close to local barometric pressure.
CLT — Coolant Temperature
Coolant Temperature. The ECU uses CLT for warmup enrichment, after-start behavior, fan control, idle behavior, and temperature-based corrections. A cold engine should usually show CLT close to ambient temperature before startup.
MAT — Manifold Air Temperature
Manifold Air Temperature. A temperature reading taken in or near the intake manifold so the ECU can estimate the temperature of the air charge entering the engine. On boosted and hot-air cars, MAT can be much higher than ambient temperature.
IAT — Intake Air Temperature
Intake Air Temperature. A general air-temperature reading used by the ECU for air-density and temperature correction. Depending on the system, IAT may be measured in the intake tube, charge pipe, air cleaner area, or intake manifold.
Lambda
Fuel mixture reference where 1.00 means stoichiometric for the fuel being used. Lambda is cleaner than AFR when fuel changes because lambda keeps the target meaning stable across gasoline, E85, alcohol, and blended fuels.
AE — Accel Enrichment
Accel Enrichment. Extra fuel added when throttle or load changes quickly. Do not tune AE until TPS, MAP, wideband scaling, and steady-state fueling are verified.
WOT — Wide Open Throttle
Wide Open Throttle. The throttle is fully open. WOT tuning should come after sensor truth, fuel pressure, injector data, base timing, warm idle, light-load behavior, and clean logs are verified.
Pull to Ground
ECU output that turns something on by completing ground. Also called low-side output or ground trigger. Related: relay, fan control, boost solenoid, and other ECU-controlled outputs.
5V Reference
A clean ECU-supplied 5V feed for sensors like TPS, MAP, fuel pressure, and oil pressure. One shorted sensor or damaged wire can drag down the whole 5V network.
Sensor Ground
The ECU’s clean reference ground for sensor signals. Do not casually treat sensor ground like dirty chassis ground. Bad grounds can make good sensors look bad.
Pull Fuel
Reduce commanded fuel in the active area. Before changing VE, identify whether the fuel error is from target lambda, trims, warmup, accel enrichment, dead time, fuel pressure, or scaling.
Throttle Stab
A quick snap of the throttle pedal. Used to observe transient response. Related: TPSdot, MAPdot, accel enrichment, wall wetting, and wideband delay.
Base Timing
The relationship between ECU-commanded timing and actual crank timing. Commanded timing must match crank timing. Verify with fixed timing mode and a timing light before tuning spark, boost, or power.
Dead Time
Injector opening delay. Wrong injector dead time creates rich/lean weirdness especially at idle and low pulse width. Do not hide wrong dead time by mangling the VE table.
Founding Access
Help build the field guide before it becomes polished.
EFI Triage is in early development. Founding Access is for people who want early access to the guide, support the project while it is being built, and help shape the first real diagnostic paths.
This is not a finished tuning course, and it is not a replacement for knowing the engine. It is a structured field guide that helps beginners slow down, verify reality, and follow the correct order instead of chasing random forum advice.
To see what is working now and what is being built next, check the Current Build Status. Questions or access issues can go to Support and Feedback.
Join Founding AccessWhat you get
- Early access to EFI Triage as the guide develops.
- Plain-English diagnostic cards and procedure branches.
- First access to ECUGN and TunerStudio-focused startup material.
- A way to support the project before it becomes a larger product.
Questions or access issues? Email [email protected].
Who this is for
Built for the person staring at the laptop, not the person pretending the laptop is the engine.
Good fit
Beginners and intermediate users working through EFI setup, first start, sensor verification, base timing, fuel pressure, idle, cruise, throttle stab, and WOT readiness.
Not a good fit
Anyone looking for magic tune numbers, blind VE table changes, or permission to skip mechanical, wiring, sensor, fuel, and timing verification.
Current focus
The first practical content path is ECUGN and TunerStudio: backup the project, verify sensors, confirm timing, enter injector data, and prove the system before tuning.
Current Build Status
EFI Triage is live, but still early.
This is the first working version of EFI Triage. The foundation is live: the guide structure, learning modes, glossary, triage trees, ECUGN / TunerStudio starter path, Stripe Founding Access, and support email are all in place.
For the longer build path, see the Roadmap. To support the early build, see Founding Access.
Working now
- Live site at efitriage.com
- Founding Access checkout
- [email protected]
- ECUGN / TunerStudio Phase One homepage path
- Starter cards for signal, fuel, timing, startup, and logging
Being built next
- Deeper card pages
- Better Cards category navigation
- ECUGN / TunerStudio standalone procedures
- TunerStudio power tools: VE Analyze, self-tune, dashboards, and log review
- DDefi dash support notes
- Printable worksheets and checklists
EFI Triage caveat: Auto-tune is not a truth machine. It is an assistant.
It can only work with the data you feed it. Verify sensors, wideband scaling, fuel pressure,
injector data, target tables, and base timing before letting software suggest tune changes.
Founding Access note
Founding Access is early access to a living guide. You are not buying a finished course yet. You are helping fund and shape the first build while getting access as it develops.
Questions or access issues? Email [email protected].
Current focus: ECUGN / TunerStudio users first. Broader ECU support comes after the first path is useful.
Phase One Index
ECUGN / TunerStudio starter path
Use this as the quick navigation path. Work from the top down unless you already know the earlier checks are verified.
How to use this page: Work top-down for a new setup. Jump by link if you are checking one system.
If a later section points back to an earlier verification step, go back and prove that step before tuning around the symptom.
Signal truth
Fuel and timing truth
Startup and road test
Fast rule: Do not tune the table, trust self-tune, or chase power until the signals feeding the ECU are believable.
First deep card
TPS — ECUGN / TunerStudio
TPS is the throttle position sensor. It tells the ECU where the throttle is. Do not tune around TPS problems. Prove the signal first.
What TPS does
TPS is used for driver intent, idle state, accel enrichment, flood clear, and throttle movement rate. It does not directly measure airflow. It tells the ECU what your foot is doing.
In TunerStudio, TPS must be calibrated so the ECU knows closed throttle and wide-open throttle.
Where to find it
TunerStudio path:
Tools → Calibrate TPS
Basic procedure:
- Key on, engine off.
- Throttle fully closed.
- Capture closed throttle.
- Press pedal fully to wide-open throttle.
- Capture WOT.
- Save and test the sweep.
Physical check before calibration
Do not calibrate TPS until the throttle system can physically move correctly. Software cannot fix a pedal, cable, linkage, or throttle blade problem.
- Remove the floormat.
- Get down and verify nothing is catching the pedal or limiting travel.
- Check carpet, pedal stop, throttle cable, linkage, brackets, clips, and return spring.
- Inspect the throttle cable for harsh bends, kinks, fraying, poor routing, or drag.
- At the throttle body, move the throttle by hand and verify it turns freely with only normal spring resistance.
- Verify the throttle blade does not catch and returns consistently.
- Connector not fully seated, wrong orientation, bent pin, pushed-out terminal, or weak sensor ground.
Turbo Buick starter reference
On many factory-style Turbo Buick scan-tool setups, closed-throttle TPS is commonly set around 0.42 volts. This is a useful starting reference, not a universal final rule.
On ECUGN / TunerStudio, still use the software calibration procedure. Teach the ECU closed throttle and WOT, then verify the TPS sweep is smooth and repeatable.
The important point is not chasing one magic number. The important point is that closed throttle, WOT, and the sweep are believable every time.
Application note: If replacing the TPS sensor, verify that the sensor is specific to the year and configuration of the car. It makes a difference.
Hot-air Turbo Buick cars do not use the same TPS application as the later 1986–1987 intercooled cars. A hot-air owner who buys the more common 1986–1987 TPS may end up with a sensor that does not fit, sweep, or operate correctly for the application.
What good looks like
- Closed throttle is stable.
- Throttle sweep is smooth.
- No sudden jumps or dropouts.
- WOT reaches full range.
- TPS returns to the same closed value.
What can fool you
- Bad sensor ground.
- Weak or noisy 5V reference.
- Check carpet and remove the mat if there is one, pedal stop, throttle cable, linkage, brackets, clips, and return spring.
- At the throttle body, move the throttle by hand and verify it turns freely with only normal spring resistance.
- Throttle cable too tight or harshly bent, kinked, routed poorly, or dragging inside the sheath.
- TPS heat drift.
- Wrong gauge or dash channel.
- DDefi dash scaling not matching TunerStudio.
- Wrong TPS for the year and configuration of the car, especially hot-air versus 1986–1987 intercooled Turbo Buick parts.
What not to tune yet
Do not tune accel enrichment yet. Do not chase a throttle-stab lean spike yet. Do not blame the VE table yet.
TPS must be calibrated and proven stable before throttle movement tuning means anything.
UI Map — You Are Here
- Software: TunerStudio
- Menu path: Tools → Calibrate TPS
- Current process step: Signal truth
- Related channels: TPS, TPSdot, RPM, MAP
- Next check: MAP — engine load
Hard stop
Do not tune accel enrichment, throttle-stab response, idle state, or VE table behavior until TPS is calibrated, physically verified, and returning consistently.
Log channels to watch
- TPS
- TPSdot
- RPM
- MAP
- AFR / Lambda
- Accel enrichment, if available
Triage branches
- TPS jumps: check sensor ground, 5V reference, wiring, and sensor condition.
- TPS does not reach full range: recalibrate and check throttle linkage/pedal travel.
- TPS changes as the car warms: check heat drift, grounding, and mechanical throttle movement.
- DDefi disagrees with TunerStudio: check dash channel assignment and scaling.
EFI Triage rule: TPS is not a fuel table. It is a signal. Verify the signal before changing the tune.
Second deep card
MAP — ECUGN / TunerStudio
MAP is manifold absolute pressure. In speed-density tuning, MAP is one of the main ways the ECU knows engine load. If MAP is wrong, the fuel and spark tables are being used in the wrong place.
What MAP does
MAP tells the ECU how much pressure is in the intake manifold. Low MAP usually means vacuum or light load. Higher MAP means more load. MAP above barometric pressure means boost.
On an ECUGN / TunerStudio setup, MAP affects fuel calculation, spark table position, datalogging, boost interpretation, and safety decisions.
Vacuum / pressure signal check
The MAP sensor needs a clean manifold vacuum and pressure signal. Do not assume any random vacuum tee is good enough.
- Use a true manifold source.
- Avoid cracked, loose, kinked, oil-soaked, or restricted hose.
- Avoid sharing the MAP signal with devices that can delay, bleed, restrict, or distort the signal.
- Watch for check valves, restrictors, boost-control plumbing, alky-control plumbing, or other devices in the same line.
- Verify the MAP signal responds quickly and smoothly when throttle and load change.
Turbo Buick MAP starter reference
Key-on engine-off MAP should be close to local barometric pressure. It does not have to read 101 kPa unless local barometric pressure is actually near 101 kPa.
On modified Turbo Buick setups, verify whether the car is using a 2-bar, 3-bar, or other MAP sensor and make sure the ECU, dash, logger, and any alcohol-control or boost-related system are using the correct signal and scaling.
If the MAP sensor range or scaling is wrong, the ECU may be using the wrong load area. That makes fuel, spark, boost, and logs suspect.
First sanity check
Key on, engine off:
MAP should read close to local barometric pressure.
At higher elevation, it will usually be lower than sea-level 101 kPa. Do not assume 101 kPa is always correct.
At idle, MAP should drop lower because the engine is pulling vacuum.
MAP signal truth: The ECU can only load the correct cells if the MAP sensor sees a clean,
direct manifold signal. A delayed, leaking, restricted, or shared signal can make the tune chase the wrong problem.
What good looks like
- Key-on engine-off MAP is close to local barometric pressure.
- Idle MAP drops into a believable vacuum range.
- MAP rises smoothly when throttle opens.
- MAP does not jump, freeze, or flatline.
- Boost readings match the installed MAP sensor range.
What can fool you
- Wrong MAP sensor range or scaling: 2-bar, 3-bar, 4-bar, or dash/logger mismatch.
- MAP sensor sharing a poor vacuum source, restricted line, check valve, leaking tee, or device that distorts the signal.
- Sensor not seeing true manifold pressure.
- Bad sensor ground or 5V reference problem.
- Dashboard showing a different channel than TunerStudio.
- Confusing boost gauge pressure with absolute MAP pressure.
What not to tune yet
Do not change VE, spark, boost control, or accel enrichment until MAP is believable.
If MAP is scaled wrong, the ECU may be looking at the wrong load cell. That makes every table decision suspect.
UI Map — You Are Here
- Software: TunerStudio
- Area: Sensor calibration / live gauges / datalog review
- Current process step: Signal truth
- Related channels: MAP, Baro, RPM, TPS, AFR / Lambda
- Next check: CLT + MAT / IAT — temperature truth
Hard stop
Do not tune VE, spark, boost control, self-tune, or throttle-response behavior until MAP scaling, wiring, and the manifold pressure source are believable.
Log channels to watch
- MAP
- Baro, if available
- RPM
- TPS
- AFR / Lambda
- Spark advance
- Boost, if shown separately
Triage branches
- MAP reads wrong key-on: check sensor calibration and local barometric pressure.
- MAP does not drop at idle: check vacuum source, hose, engine vacuum, and sensor wiring.
- MAP jumps or drops out: check wiring, sensor ground, 5V reference, and connector condition.
- Boost reading is wrong: confirm MAP sensor range and absolute pressure versus gauge pressure.
EFI Triage rule: MAP tells the ECU where the engine is loaded. If MAP lies, the tune follows the lie.
Third deep card
CLT + MAT / IAT — ECUGN / TunerStudio
CLT and MAT are temperature signals. CLT tells the ECU engine coolant temperature. MAT or IAT tells the ECU intake air temperature. If these readings are wrong, startup, warmup, fueling corrections, fan control, and heat-related decisions can all be wrong.
What CLT does
CLT is coolant temperature. The ECU uses it for warmup enrichment, after-start behavior, fan control, idle behavior, safety logic, and temperature-based corrections.
A cold engine should show a CLT value close to ambient temperature before startup.
What MAT / IAT does
MAT or IAT is intake air temperature. The ECU uses it for air-density correction and heat-related tuning decisions.
On a hot-air turbo Buick, MAT is not decoration. It is part of the engine’s survival margin.
Temperature sanity check
Before startup, CLT and MAT / IAT should usually read close to ambient temperature if the car has been sitting. They do not need to be identical, but they should be believable for the conditions.
- Very cold readings can point to an open circuit, unplugged sensor, wiring issue, or wrong calibration.
- Very hot readings can point to a short, wiring issue, wrong calibration, heat soak, or actual hot air.
- Sudden jumps or flatlined values should be treated as sensor, wiring, or calibration problems before tuning.
- Verify the sensor type and calibration curve before changing warmup or air-temperature corrections.
Hot-air MAT reality check
On hot-air and heat-soaked boosted combinations, MAT / IAT can be much higher than ambient. Readings in the 120–180°F range can happen depending on heat soak, airflow, boost, sensor location, underhood heat, and intake layout.
A high MAT reading is not automatically a bad sensor or a bad tune. First decide whether the air charge is actually hot, whether the sensor location is heat soaked, or whether the reading is caused by wiring, calibration, or sensor error.
Hot-air Turbo Buick MAT sensor location
On hot-air Turbo Buick applications, a useful MAT / IAT location may be the front of the intake manifold, near the plugged boss / hex plug area by the CLT sensor. This location can place the sensor closer to the actual air charge entering the engine.
A long-nose MAT / IAT sensor may be preferred so the sensing element reaches into the air stream instead of mainly reading heat-soaked metal.
Verify thread size, sensor depth, sealing, clearance, connector, calibration, and wiring before installation.
Sensor range and calibration
A standard / Lo-IAT sensor may be appropriate for manifold MAT on many hot-air Turbo Buick setups because it has good resolution in the range where the engine normally operates. A Hi-IAT sensor may be useful for hotter locations or compressor-outlet-style measurement.
Do not install an IAT sensor just because the thread fits. The ECU calibration must match the exact sensor curve, and the sensor temperature range must match the environment it will see.
What good looks like
- Cold CLT and MAT are close to ambient temperature.
- CLT rises smoothly as the engine warms.
- MAT responds logically to heat soak and airflow.
- No sudden jumps, flatlines, or impossible values.
- Fan behavior matches the CLT reading and fan settings.
What can fool you
- Wrong thermistor calibration or wrong sensor curve.
- Wrong sensor version for the temperature range being measured.
- Sensor location reading heat-soaked metal or stagnant air instead of the air charge.
- Open circuit, shorted wire, bad connector, or weak sensor ground.
- MAT / IAT reading real hot air, not a bad sensor or bad tune.
- Heat soak, hot-air plumbing, intercooling, alcohol injection, or underhood airflow changing what MAT / IAT reports.
What not to tune yet
Do not tune warmup enrichment, after-start enrichment, MAT correction, or fan behavior until the temperature readings are believable.
Do not use the VE table to hide a cold-start or temperature-sensor problem.
UI Map — You Are Here
- Software: TunerStudio
- Area: Sensor calibration / live gauges / warmup behavior
- Current process step: Temperature truth
- Related channels: CLT, MAT / IAT, RPM, MAP, AFR / Lambda, warmup enrichment
- Next check: Wideband / Lambda — fuel result truth
Hard stop
Do not tune warmup enrichment, after-start enrichment, MAT correction, fan control, or cold-start behavior until CLT and MAT / IAT readings are believable.
Log channels to watch
- CLT
- MAT / IAT
- RPM
- MAP
- AFR / Lambda
- Warmup enrichment
- After-start enrichment, if available
- Fan output state, if available
Triage branches
- CLT reads very cold: check unplugged sensor, open circuit, wiring, and calibration.
- CLT reads very hot: check short to ground, wrong calibration, or wiring fault.
- MAT is heat soaked: separate real hot-air behavior from sensor/wiring problems.
- Fan does not act correctly: verify CLT reading before changing fan settings.
EFI Triage rule: Temperature corrections only help if the temperature readings are true.
MAT truth: High MAT is not automatically wrong. Judge it against ambient temperature,
sensor location, heat soak, airflow, boost, and the car's intake system. If the air is really hot,
respect the temperature before tuning around it.
Fourth deep card
Wideband / Lambda — ECUGN / TunerStudio
The wideband tells you the fuel result. It does not tell you why the result happened. Before using wideband data to change the tune, prove the gauge, ECU input, calibration curve, fuel display, and log all agree.
What the wideband does
A wideband oxygen sensor measures the exhaust oxygen content and reports mixture as AFR or lambda. The ECU can use this for datalogging, closed-loop correction, VE Analyze, and safety review.
A wideband is a truth tool only when it is wired, powered, grounded, calibrated, and interpreted correctly.
Lambda vs AFR
Lambda is the cleaner way to think when fuel changes. Lambda 1.00 means stoich for the fuel being used. Richer than stoich is below 1.00. Leaner than stoich is above 1.00.
AFR numbers change with gasoline, E10, E85, methanol, and blended fuels. Lambda keeps the target meaning stable.
What good looks like
- Wideband controller powers up and warms normally.
- Gauge and TunerStudio agree closely.
- Log value matches the live TunerStudio value.
- Reading changes smoothly with fuel and load changes.
- No impossible fixed, pegged, or delayed values.
What can fool you
- Wrong 0–5V calibration curve.
- Analog ground offset.
- Gauge set to AFR while ECU/log is using lambda, or the reverse.
- Fuel type changing the meaning of AFR numbers.
- Exhaust leak near the sensor.
- Sensor not warmed up or sensor aging/failure.
What not to tune yet
Do not use VE Analyze, closed-loop correction, or wideband-based fueling changes until the wideband input is verified.
Do not change the VE table just because the gauge and ECU disagree. First find out which one is wrong.
Log channels to watch
- AFR / Lambda
- AFR target / Lambda target
- EGO correction
- RPM
- MAP
- TPS
- Pulse width
- Battery voltage
- Fuel pressure, if available
Triage branches
- Gauge and ECU disagree: check 0–5V curve, analog ground, and ECU calibration.
- Reading is stuck rich or lean: check sensor warmup, wiring, controller status, and exhaust leaks.
- Lambda looks right but AFR looks wrong: check fuel stoich and display convention.
- VE Analyze makes ugly changes: verify wideband, target table, injector data, and fuel pressure first.
EFI Triage rule: The wideband shows the result. It does not prove the cause.
Fifth deep card
Fuel Pressure — ECUGN / TunerStudio
Fuel pressure proves whether the injectors are being fed the pressure the tune assumes. If fuel pressure is wrong, the wideband result may be real, but the cause may not be the VE table.
What fuel pressure does
Injector flow depends on pressure difference across the injector. The tune assumes a certain injector size at a certain base fuel pressure. If actual pressure is different, actual fuel delivery is different.
On a boosted engine, fuel pressure should normally rise with boost when using a boost-referenced regulator.
First sanity check
Key on / pump running:
Confirm base fuel pressure with a gauge before blaming the tune.
Vacuum / boost reference:
Verify the regulator reference line is connected, dry, and seeing true manifold pressure.
What good looks like
- Base pressure matches the tune/injector assumption.
- Pressure is stable at idle and cruise.
- Pressure rises with boost on a boost-referenced system.
- No fuel leaks.
- Pressure does not fall off under load.
What can fool you
- Weak fuel pump or poor pump voltage.
- Restricted filter or line.
- Return-line restriction causing pressure control problems.
- Regulator reference hose disconnected or leaking.
- Gauge error or sensor scaling error.
- Trying to fix fuel-pressure problems with the VE table.
What not to tune yet
Do not tune boost fueling, WOT lambda, or VE table shape until fuel pressure is known and stable.
If pressure drops under load, adding fuel in the table may only hide the real problem until the system runs out of pump or injector.
Log channels to watch
- Fuel pressure, if logged
- MAP / boost
- AFR / Lambda
- AFR target / Lambda target
- Pulse width
- Injector duty cycle
- Battery voltage
- RPM
Triage branches
- Pressure too high: check regulator, return restriction, reference line, and base setting.
- Pressure too low: check pump, filter, voltage, wiring, and supply restriction.
- Pressure drops under boost: stop WOT testing and verify pump capacity, voltage, filter, lines, and regulator.
- Logged pressure disagrees with gauge: check pressure sensor scaling and wiring.
EFI Triage rule: Fuel pressure is not a guess. Verify it before blaming the tune.
Sixth deep card
Injector Data / Required Fuel — ECUGN / TunerStudio
Injector data tells the ECU how much fuel the injectors can deliver and how they behave electrically. If injector size, dead time, fuel pressure, or fuel type assumptions are wrong, the whole fuel model is wrong.
What injector data does
The ECU calculates fuel delivery from engine size, injector size, fuel type, air load, VE, target mixture, and correction tables. Injector data is part of that foundation.
Required Fuel is not the whole tune. It is a base calculation. The VE table works on top of that base.
What must be known
- Injector size.
- Fuel pressure used to rate the injector.
- Actual base fuel pressure on the car.
- Injector dead time / battery voltage correction.
- Fuel type or stoich value.
- Sequential, semi-sequential, batch, or other injection strategy.
What good looks like
- Injector size matches the actual installed injectors.
- Fuel pressure assumption matches measured fuel pressure.
- Dead time data is from a trusted source when possible.
- Idle pulse width is believable.
- VE table does not need ugly numbers to hide bad setup data.
What can fool you
- Injectors advertised at one pressure but used at another.
- Unknown or fake injector flow data.
- Wrong dead time making idle and low-load fueling unstable.
- Fuel pressure not matching the tune assumption.
- Changing fuel type without updating stoich/fuel settings.
- Using the VE table to cover up bad injector data.
What not to tune yet
Do not start shaping the VE table aggressively until injector size, fuel pressure, and basic injector behavior are reasonable.
If injector data is wrong, every fuel correction after it becomes suspicious.
Log channels to watch
- Pulse width
- Injector duty cycle
- Battery voltage
- AFR / Lambda
- AFR target / Lambda target
- EGO correction
- MAP
- RPM
- Fuel pressure, if available
Triage branches
- Rich idle: check injector size, dead time, fuel pressure, and wideband scaling before lowering VE.
- Lean under load: check fuel pressure, injector duty cycle, pump voltage, and injector capacity.
- VE table looks ugly: check injector data, MAP scaling, wideband scaling, and fuel pressure.
- Fueling changes with voltage: check injector dead time and battery voltage correction.
EFI Triage rule: Do not use the VE table to hide bad injector data.
Seventh deep card
Base Timing Verification — ECUGN / TunerStudio
Base timing verification proves that the timing commanded by the ECU matches the actual timing at the crank. If commanded timing and crank timing do not agree, the spark table cannot be trusted.
What base timing verification does
The ECU may command a timing value, but the engine only cares what happens at the crankshaft. A timing light is used to compare commanded timing to actual crank timing.
This must be verified before tuning ignition, boost, knock response, or power.
Basic procedure
- Warm the engine enough to idle safely if possible.
- Set the ECU to fixed / locked timing mode.
- Command a known timing value.
- Use a timing light on the crank.
- Compare crank timing to commanded timing.
- Correct trigger offset or setup if needed.
- Recheck before returning to normal timing mode.
What good looks like
- Commanded timing matches crank timing.
- Timing mark is stable.
- Timing does not drift with RPM.
- No sync-loss or trigger errors during the check.
- Normal timing mode is restored after verification.
What can fool you
- Wrong trigger offset.
- Wrong ignition output setting.
- Wrong timing light setup.
- Timing mark or balancer mark not trusted.
- Unstable crank/cam signal.
- Forgetting to turn fixed timing mode back off.
What not to tune yet
Do not tune spark advance, boost timing, knock response, or power if base timing is not verified.
If the crank does not match the laptop, the spark table is fiction.
Log channels to watch
- Spark advance
- RPM
- MAP
- TPS
- Battery voltage
- Sync loss / lost sync count
- Crank/cam status, if available
Triage branches
- Timing does not match: check trigger offset, ignition settings, and timing light setup.
- Timing mark jumps: check sync, crank/cam signal, wiring, and ignition stability.
- Timing drifts with RPM: check trigger settings, sensor polarity, and ignition configuration.
- Engine runs worse after check: confirm fixed timing mode was turned back off.
EFI Triage rule: If the timing light disagrees with the laptop, believe the timing light.
Eighth deep card
First Start Checklist — ECUGN / TunerStudio
First start is not the time to tune for power. First start is for proving the engine runs, the ECU sees believable data, the fuel system is safe, timing is verified, and nothing is leaking, overheating, or lying.
Before cranking
- Tune/project backed up.
- Battery charged and stable.
- ECU connects in TunerStudio.
- TPS calibrated and smooth.
- MAP reads believable key-on.
- CLT and MAT read believable cold.
- Wideband powers up and is configured.
- Fuel pressure checked.
- Injector data entered.
- Base timing verification plan ready.
During first start
- Watch oil pressure.
- Watch fuel pressure.
- Watch AFR / lambda for sanity.
- Watch coolant temperature.
- Watch battery voltage.
- Watch RPM and sync behavior.
- Listen for mechanical problems.
- Look for fuel, oil, coolant, and exhaust leaks.
- Do not rev it to “see how it sounds.”
What good looks like
- Engine starts and stays running long enough to observe data.
- Oil pressure comes up quickly.
- Fuel pressure stays stable.
- CLT rises normally.
- AFR / lambda is believable.
- No major leaks or alarming noises.
Stop immediately if
- No oil pressure.
- Fuel leak.
- Coolant leak or fast overheating.
- Severe lean condition.
- Severe rich/flooding condition.
- Timing is clearly wrong.
- Knock, backfire, mechanical noise, or sync loss appears.
What not to tune yet
Do not tune boost. Do not tune WOT. Do not chase perfect idle yet. Do not start changing several tables at once.
First start is for proving the basics and finding obvious problems.
Log channels to watch
- RPM
- MAP
- TPS
- CLT
- MAT / IAT
- AFR / Lambda
- Fuel pressure, if available
- Battery voltage
- Spark advance
- Pulse width
- Sync loss / lost sync count
Triage branches
- No start: check ECU power, RPM signal, sync, fuel pressure, injector pulse, and spark.
- Starts then dies: check after-start enrichment, idle air, MAP, fuel pressure, and timing.
- Runs very rich: check injector data, fuel pressure, wideband scaling, and warmup enrichment.
- Runs very lean: check fuel pressure, injector setup, vacuum leaks, and wideband scaling.
EFI Triage rule: First start is not a victory lap. It is a controlled systems check.
Ninth deep card
Warm Idle Checklist — ECUGN / TunerStudio
Warm idle comes before cold-start tuning. Get the engine fully warm, prove the sensors are stable, and make sure the idle system is not fighting the fuel and timing tables.
What warm idle proves
Warm idle shows whether the engine, throttle position, MAP signal, injector setup, AFR / lambda reading, timing, idle air, and basic VE table are close enough to continue.
If warm idle is unstable, cold start and driveability tuning will be harder and less reliable.
Before tuning idle
- Engine is fully warm.
- CLT reading is believable.
- MAT / IAT reading is believable.
- TPS is calibrated and stable.
- MAP is stable and believable.
- Wideband input is verified.
- Fuel pressure is verified.
- Base timing has been checked.
What good looks like
- RPM is stable or only moves slightly.
- MAP is stable for the engine combination.
- AFR / lambda is believable and controllable.
- Timing is stable and reasonable.
- Idle air control is not hunting wildly.
- Battery voltage is stable.
What can fool you
- Vacuum leak.
- Throttle blade open too far or not far enough.
- TPS not returning to closed value.
- Injector dead time wrong.
- Fuel pressure wrong.
- Wideband scaling wrong.
- Idle timing control fighting idle air control.
What not to tune yet
Do not tune cold start yet. Do not tune accel enrichment yet. Do not tune boost yet.
Warm idle is the stable reference point. Fix warm idle before chasing cold-start behavior.
Log channels to watch
- RPM
- MAP
- TPS
- CLT
- MAT / IAT
- AFR / Lambda
- AFR target / Lambda target
- EGO correction
- Spark advance
- Idle valve position, if available
- Battery voltage
- Pulse width
Triage branches
- Idle hunts: check idle air control, timing control, AFR swing, and vacuum leaks.
- Idle is rich: check injector dead time, fuel pressure, wideband scaling, and VE cell.
- Idle is lean: check vacuum leak, fuel pressure, injector setup, and VE cell.
- Idle changes when fan turns on: check battery voltage, grounds, alternator output, and idle compensation.
EFI Triage rule: Tune warm idle before cold start. Tune stability before response.
Tenth deep card
First Drive / Light Load Checklist — ECUGN / TunerStudio
The first drive is not for boost or hero pulls. It is for proving that the engine behaves under light load, the sensors stay believable, the wideband result follows the target, and the tune responds predictably.
Before the first drive
- Warm idle is stable.
- TPS, MAP, CLT, MAT, and wideband are verified.
- Fuel pressure is known.
- Injector data is reasonable.
- Base timing is verified.
- No fuel, oil, coolant, or exhaust leaks.
- Brakes, throttle return, and charging system are safe.
- Logging is ready before the car moves.
What to do first
- Start with gentle throttle only.
- Keep boost out of it.
- Hold steady light-load areas when safe.
- Watch AFR / lambda against target.
- Watch MAP, TPS, RPM, and coolant temperature.
- Return and review the log before making changes.
What good looks like
- Throttle response is predictable.
- MAP follows load smoothly.
- AFR / lambda is close enough to target for light load.
- Coolant temperature stays controlled.
- No sync loss, misfire, knock, or voltage drop.
- The log matches what the driver felt.
What can fool you
- Wideband delay during quick throttle changes.
- Accel enrichment being mistaken for VE error.
- Closed-loop correction hiding a bad base table.
- Heat soak changing MAT.
- Voltage drop affecting injector behavior.
- Trying to tune too many areas from one messy drive.
What not to tune yet
Do not tune WOT. Do not turn up boost. Do not chase every small transient spike.
First-drive tuning is about light-load confidence and clean data, not maximum power.
Log channels to watch
- RPM
- TPS
- MAP
- AFR / Lambda
- AFR target / Lambda target
- EGO correction
- Pulse width
- Injector duty cycle
- Spark advance
- CLT
- MAT / IAT
- Battery voltage
- Fuel pressure, if available
- Sync loss / lost sync count
Triage branches
- Lean at steady light load: check VE cell, target table, wideband scaling, fuel pressure, and EGO correction.
- Lean only when throttle moves: check TPSdot, MAPdot, accel enrichment, and wideband delay.
- Rich everywhere: check injector data, fuel pressure, dead time, and warmup correction.
- Misfire or breakup: stop and check ignition, plugs, wires, sync, fuel pressure, and voltage.
EFI Triage rule: First drive is a data-gathering test, not a power test.
Eleventh deep card
Datalog Review Order — ECUGN / TunerStudio
A datalog is not one number. Read the event in order. Find what happened, when it happened, what changed first, and which signals can be trusted before changing the tune.
Why order matters
Beginners often stare at AFR / lambda first. That is useful, but it is only the result. Before blaming fuel, check what the engine and ECU were doing at that exact moment.
A lean spot can come from VE, fuel pressure, accel enrichment, injector limit, voltage drop, wrong MAP scaling, wideband delay, or bad sensor data.
Read the log in this order
- RPM
- TPS
- MAP / boost
- AFR / lambda
- AFR target / lambda target
- EGO correction
- Pulse width
- Injector duty cycle
- Spark advance
- Knock / knock retard, if available
- CLT
- MAT / IAT
- Battery voltage
- Fuel pressure, if available
- Sync loss / lost sync count
What good looks like
- The log matches what the driver felt.
- Sensor values move smoothly and logically.
- AFR / lambda can be compared to target.
- Corrections are not maxed out or hiding a bad base setup.
- No unexplained voltage drop, sync loss, or signal dropout.
What can fool you
- Wideband delay during throttle movement.
- Closed-loop correction hiding the real base fuel error.
- Looking at AFR without checking target.
- Ignoring TPSdot / MAPdot during transient events.
- Calling false knock before proving it is false.
- Making changes from a messy or unsafe log.
What not to change yet
Do not change multiple tables from one unclear log. Do not tune from a log with bad sensor data.
One clean log with a clear event is better than ten messy logs with guesses.
Fast triage questions
- What was the driver doing?
- What changed first: TPS, MAP, AFR, voltage, or sync?
- Was the event steady-state or transient?
- Was AFR / lambda compared to target?
- Was closed-loop correction active?
- Was fuel pressure known?
- Did the ECU lose sync or voltage?
Triage branches
- Lean only during throttle movement: check TPSdot, MAPdot, AE, and wideband delay.
- Lean at steady load: check VE, target, fuel pressure, injector duty, and EGO correction.
- Rich everywhere: check injector data, fuel pressure, dead time, and wideband scaling.
- Breakup or misfire: check ignition, plugs, wires, sync, voltage, and fuel pressure.
EFI Triage rule: Read the event before changing the tune.
ROADMAP
Build path
EFI Triage will grow in stages. Founding members help shape which confusing areas get mapped first.
For what is working today, see Current Build Status. To support the early build, see Founding Access. For questions or access issues, use Support and Feedback.
Now building
- Beginner glossary
- EFI triage cards
- Order of operations
- ECUGN / TunerStudio starter path
- No-start and sensor verification trees
Next
- DDefi dash support map
- AEM wideband setup notes
- Printable worksheets
- First-start checklist
- First-log review guide
Later
- Holley EFI
- HP Tuners
- Haltech
- FuelTech
- AI Triage Assistant
- Printable field guides
- Vendor and tuner resource hub with required setup data: ranges, wiring, calibration, fitment, settings, caveats, and support links
Vendor inclusion rule: EFI Triage listings must provide useful setup data.
A product link without range, wiring, calibration, fitment, settings, and caveats is not enough.
Paid placement may buy visibility, but it does not buy the diagnostic logic.
CONTACT
Support and feedback
EFI Triage is being built around real confusion points: lingo, UI location, wiring basics, process order, and diagnostic branches.
Need help or found a confusing area?
For the fastest help, include your ECU, tuning software, support electronics, what you have already verified, and the exact symptom. Useful details include whether the issue happens at idle, cruise, throttle stab, first start, warm restart, boost, or WOT.
- ECU / ECM and tuning software
- Support electronics: dash, wideband, logger, flex fuel, boost control
- Verified checks: TPS, MAP, CLT/MAT, wideband, fuel pressure, base timing
- Exact symptom and when it happens
- Log or screenshot if available
Send support and founding-member questions to:
This email is active. Better information makes triage faster.
Refund / early-access note
Founding Access supports an early-stage build. EFI Triage is live and useful, but it is not a finished course, complete manual, or one-on-one tuning service yet.
If you joined by mistake or expected a finished product, email [email protected] and the issue will be reviewed fairly.
Full terms, refund policy, and member access details will be expanded as the platform develops.
Paid rollout
Cheap enough to help, paid enough to build infrastructure.
Start with a free sample library and a low-cost paid ECUGN / TunerStudio beta. Add AI triage only after the content system is solid.
Free
Sample glossary, intro cards, mission, sample triage.
$0Founding Beta
Full starter guide, ECUGN / TunerStudio cards, checklists, feedback access.
$49/yearJoin Founding AccessECU Guide
Product-specific UI maps, PDFs, support-electronics add-ons.
$89/year