FAQ¶

Common symptoms and where to look. Most problems trace back to one or two pages.

Why won't it start when cold?¶

A cold engine needs extra fuel and cranking time. Check, in order:

The start sequence — ignition on (E) first, and wait for FUEL PRESSURE to fill; then hold crank (R) and keep your hands off the throttle. See Starting an Engine.
Cranking enrichment — the cold end of the curve may be too low (won't catch) or too high (floods). If it fires then drowns, reduce it.
It floods — the state window shows FLOODED. Hold the throttle above 75 % while cranking until it clears, then release.
A weak battery — watch VOLTAGE while you crank. See Battery Voltage.

Why is it hunting at idle?¶

RPM swinging up and down at idle usually comes from one of:

An erratic idle VE cell — common with an aggressive cam, whose overlap makes idle airflow choppy. Stabilize fuelling first.
An idle target below the cam's stable floor — see Cold Idle.
The idle control closed-loop gains being too aggressive.
A light crank/flywheel — less inertia means a busier idle the controller must manage.

Why is there no power up top?¶

If the engine flattens out near the top of the rev range:

Injectors maxed — when demand reaches their capacity the mixture leans out, acting like a soft rev limit. Check whether the throttle-box FUEL cell stops rising while λ drifts lean.
Hitting your rev limiter — the limit you set may simply be where it stops.
Valve float — past the head's RPM limit VE collapses.
Breathing — the head, cam, intake, and exhaust may not flow at high RPM.
Timing pulled by knock — if knock control is retarding, you'll lose top-end power.

Why does it run rich when warm?¶

Often an enrichment curve that doesn't fully taper out:

Warmup enrichment must reach 1.0× at operating temperature (60 °C by default). Check that the curve actually gets to 1.0×.

Why did it suddenly go lean under load?¶

If injectors aren't maxed, suspect fuel pressure sagging — watch the FUEL PRESSURE bar. Low pressure also disables closed-loop.

Why is it knocking?¶

Knock rises with load, heat, and advance, and falls with octane and richer mixtures. On a hot day or low octane, pull timing or richen the mixture.

Why do I get "OPEN (ENRICH)" or "OPEN (TRANSIENT)"?¶

Those are closed-loop badges — it's switched itself off on purpose. OPEN (ENRICH) means a deliberate enrichment is active (cranking, after-start, warmup, acceleration or wall-film correction), so feedback would fight it. OPEN (TRANSIENT) means the engine is changing too fast for the delayed lambda sensor to be trusted. Closed loop also waits 0.9 s after any condition clears before it comes back.

Why did my engine stop after I changed a part?¶

Changing any part rebuilds the engine: it stops (ignition off, neutral), temperatures reset to ambient and wear resets to new. See Engine Setup.

The engine won't rev past a certain RPM¶

Check, in order:

Your rev limiter setting.
An injector ceiling — the mixture leans out near the top.
Valve float past the head's limit.
Limp mode (warning light 7), which caps RPM at 3000 — see Damage & Wear.

Everything is greyed out¶

You're probably in the demo build. See Demo vs Full Version.