Cold Idle¶
A raised idle target while the engine is cold, falling toward normal idle as coolant warms up.
What it is¶
A cold engine is mechanically reluctant: oil is thick, fuel vaporizes poorly, and friction is high. Cold idle (fast idle) raises the target idle RPM while the engine is cold, then lowers it toward the normal target as coolant warms. In Engone the target runs from roughly 2000 RPM at −20 °C down to about 850 RPM at 90 °C.
This is a target for the idle control system, which holds it by adjusting the throttle blade — it isn't extra fuel (that's warmup enrichment).
Why it matters¶
- A higher idle gives the cold engine the airflow and energy it needs to avoid stalling when it's most fragile.
- The extra RPM and load speed up warmup, getting the engine to operating temperature (and out of enrichment) sooner.
If cold idle is set too low, a cold engine stalls at rest; too high, and it races uncomfortably and warms slowly to the right RPM.
How to tune it¶
Shape the target curve against coolant temperature: high at the cold end, smoothly reaching the normal idle target at operating temperature. Pair it with warmup enrichment so the cold engine has both the air (idle target) and the fuel it needs.
Rule of thumb
Set the cold target just high enough to idle rock-steady without throttle input from cold — higher than that only wastes fuel and noise.
In the game¶
The cold-idle target curve is on the Fuel page. Watch idle RPM step down as the coolant gauge climbs toward operating temperature.