Hi Guys,

I have a Warm-Start Idle Stumble issue.

Running a Comp 268XFI on a 111 LSA. 50 degrees of seat overlap.

The engine size is a 355.

The car runs pretty good warm (just part throttle cruzing at this point).

During a warm start, I have to jab the throttle twice to stabilize the engine RPM at the set-point.

Please reference the attached data log graphs.

The engine starts at the commanded RPM and then falls until I hit the throttle once or twice to stabilize the idle RPM.

I notice 2 interesting events.

1.
For some reason the IAC counts go from 145 at the initial start to 80.

Could this be the root cause of the whole event?

What parameters would effect this transcient behavior?

The warm idle (about 950 RPM) IAC counts is around 30 and port vacum is around 13-14 " hg.

2.
As the RPM drops, the LV8 increases and the SA drops. This follows the SA_vs_RPM_vs_LV8 table.

Also, the SA_Comp_vs_Coolant_Temp table appears to be pulling roughly 5 degrees of timing at a 90 degree warm start coolant temp.

Could the lower SA value cause the idle instability?

Not sure what event is the root cause?

The IAC event occurs first.

3.
I noticed that a Start-Up SA vs Coolant temp table exists.

When does the ECU switch from this table to the regular SA tables?

What parameter controls this switch-over point?

Any help would be appreciated.

Best Regards,

Bruce