Cold Start Idle

[War Bird]

My car has had trouble with holding an idle after cold start after I installed a set of PRC225 heads, a Fast 92, and TSP Torquer II cam around 2.5 years ago now. I had a local shop tune it, and have kind of just lived with the issue since.

Basically, You have to feather the throttle or hold the RPM above 1000 until the car warms up (in the attached file it looks like 73 degrees was the point it was able to maintain an idle...You can see where it stalled just prior to this).

Once the car is warmed up, it holds idle fine. I'm not sure which table to even look at here, as there appear to be several associated with idle throughout the ECT range during start up.

Searching turns up a lot of threads on a hard cold start condition rather than trouble holding idle immediately after start.

Appreciate a point in the right direction.

Thanks!

[kevin87turbot]

Add the IAC position to the datalog and get us another cold start log and a hot idle log.

[War Bird]

Add the IAC position to the datalog and get us another cold start log and a hot idle log.

Will do. I'll try and get one posted tomorrow.

[Matt Vardaman]

Your Base Running airflow looks like it could be contributing to the problem, it Starts out excessively high then falls off too fast to something normal when warmed up. I would interpolate the values between -40 and 176. You might turn on Short term fuel trims in Open loop in the fuel open loop tab. You can change Frictional Airflow delay to 50 camshaft revolutions - idle>airflow>frictional airflow delay. Try some of these changes and let me know if it starts better.

[War Bird]

Add the IAC position to the datalog and get us another cold start log and a hot idle log.

Please see attached log with IAC position and IAC desired position logged. FYI, I did alter the Base Running Airflow table, interpolating between -40 and 176 to bring the values down as suggested by Matt, and did see some improvement off the bat.

Your Base Running airflow looks like it could be contributing to the problem, it Starts out excessively high then falls off too fast to something normal when warmed up. I would interpolate the values between -40 and 176. You might turn on Short term fuel trims in Open loop in the fuel open loop tab. You can change Frictional Airflow delay to 50 camshaft revolutions - idle>airflow>frictional airflow delay. Try some of these changes and let me know if it starts better.

So far all I did was interpolate between -40 and 176 and it did start and hold idle with no throttle input (stumbled a little but recovered on its own and held it). Before I mess with the other tables you suggested, Is there some kind of error calc that can be applied to this table to further tune the base running airflow? Right now I'm logging MAF and "Desired AF", not sure if that is the right approach.




Thanks guys!