I'm not entirely sure what my issue is. Sometimes my car falls flat on its face on rapid deceleration. I put a new ACDelco IAC p/n 217415 last year and the problem still shows up intermittently. So I sent the TPI TB off to Dr Injector for a full rebuild. It did have a sloppy shaft which is no longer the case. Still stalls on decel sometimes. So now I'm starting to think my IAC is just not quite up to par. I thought I'd just throw another one in there and see if I just got a bad one last time around. Anyway...I see 2 ACDelco parts that are listed for my car. (91 Z28 305 T5). The 217415 that is in it now and they also show a p/n 217437. Does anyone know what the difference is between these 2 part numbers? Are they interchangeable? It looks like ACDelco #217437 is the replacement for the original GM#25527077 and ACDelco #217415 is for 217415 GM#17112193. Problem is, I have no idea what the original part was on a 24 year old car that has probably had the part replaced multiple times during different periods of ownership.

 

If you have not done so-please adjust the minimum idle air to TB.

(using scan tool monitor IAC position(counts) with car fully warmed up ,you should have 10-20 IAC.. if counts to high -open TB blades-..

this can cause the issues you are having..

GL
Mike

 

I've done that minus the IAC count monitor. I don't have a scan tool or access to one so I'm forced to swap out parts.

 

I remember reading a thread on here about a year ago about the different IAC part numbers. I think the springs are slightly different between the two. Unfortunately, I can't help you determine which one is correct for your car.