Cold Start Rumble

[jaydaniels]

Awesome info. Thanks. Sounds like the rumble may be due to a low idle setting causing a lean condition. If warming the coolant helped my sled start then I would say it essentially richened the mixture by reducing the amount of air induced by the iac. Make sense?

 

[dubla92]

Awesome info. Thanks. Sounds like the rumble may be due to a low idle setting causing a lean condition. If warming the coolant helped my sled start then I would say it essentially richened the mixture by reducing the amount of air induced by the iac. Make sense?

You're welcome. But the low idle speed setting causes a rich mixture due to the IAC not allowing as much air as the ECU is calibrated for. So if the idle speed is set to low then the IAC passes less air when cold. When the ECU injects its " mapped" amount of fuel it is too much and then the machine may not start due to the rich condition, fouling the plugs. When the machine sits while you warm up the thermostat housing, the combustion chamber dries and the heat gun raises the Engine temp reading the ECU sees and then the ECU injects less fuel. Remember the ECU injects the most fuel during a cold start. The ECU does not know the idle setting nor can it compensate for a low set idle speed setting. It is mapped to inject fuel based on an idle speed setting of 1500RPM.

Hope this all helps.

 

[jaydaniels]

Ok that makes sense. Thanks again.