Random stutter/misfire at idle - particularly when changing to neutral/park

[PappaYeet]

Timing chain is a possibility. It’ll have to be done one day but the issue isn’t bad enough to really justify the effort right now.

 

[PappaYeet]

Is it true that the L67 and Ecotec have different IAC Valves? If so, how can you tell/what are the part numbers? It wouldn't surprise me if the previous owner replaced it with the wrong (ie cheaper) one in the past, as he did with many parts.

 

[Immortality]

No. There are 2 different sizes, the larger size IAC was used in the later model cars ecotec and L67.

I did post a pic of the 2 differences somewhere in a thread but I'll have to find it.

 

[PappaYeet]

I’ve had a look and I’ve found 2 with conical tips, one with the spring covered and one without. There’s also one with a much flatter tip. All of them say that they’re suitable for the L67 so not sure what’s going on there.

I know that my current one has the shiny conical tip with the spring uncovered.

 

[Immortality]

The primary difference is the pintle size and the corresponding size increase in the IAC passages in the TB.

I've seen stepper motors both with and without the little pastic cover over the spring, I think it was added to reduce the contamination issue you see with gunk up throttle bodies and stepper motors stuffing up the idle.