Can't nail start-up RAF

[Patrick G]

Maybe I'm going about it the wrong way.

My long term idle trims are pretty close to 0% and my short term idle trims look good except for startups...especially hot re-starts.

My short term idle trims are in the +2 g/sec at hot restart even though my LTIT are low. What affects this more? Idle Airflow Parked Position {B4308}? Startup idle airflow correction {B4303}? Startup Friction Airflow Correction {B4343}? FWIW, my values are raised above stock for B4308 and B4303.

Does the positive number mean I'm not getting enough airflow and the PCM is needing to add more? Thanks in advance.

[jnorris]

Mine does the same thing. The value is coming from the Startup Friction Airflow Correction {B4343} table. As soon as this value zeros out it is transferred to the short term idle trim in drive and park/neutral. Leaving the car in park it takes the short term idle trim about 30s to return to “normal”. When I put the car in drive the IAC numbers and idle jump up responding to the high number in the short term idle trim and within 30s the short term idle trim return to “normal”. All is good until I turn the car off and restart it.

John