I just bought a '88 Iron Duke and I'm super happy to be a part of the fiero community.
Picking it up I knew that it would have some issues (as I got it for a steal of a price) but when it's running and driving it does super well.
The issue I want to diagnose right now is that the engine oftentimes doesn't want to idle- it wants to sputter out and stall.
I started replacing vacuum lines- and I know I've fixed a pretty good handful of leaks already. I wouldn't be surprised if there were more, but I don't know for sure.
My Fiero is also throwing a code 45, rich exhaust, and I'm wondering if the engine stalling and the code are correlated.
My potential thoughts right now are that I need to clean/replace the O2 sensor, check for more vacuum leaks, and potentially mess with the IAC..?
Problem is- I'm totally new to this kind of stuff and I have no idea where to look for the IAC.

If anybody has any suggestions on how to fix the stalling idle please let me know!

quote Originally posted by abitsma: I just bought a '88 Iron Duke and I'm super happy to be a part of the fiero community. Picking it up I knew that it would have some issues (as I got it for a steal of a price) but when it's running and driving it does super well. The issue I want to diagnose right now is that the engine oftentimes doesn't want to idle- it wants to sputter out and stall. I started replacing vacuum lines- and I know I've fixed a pretty good handful of leaks already. I wouldn't be surprised if there were more, but I don't know for sure. My Fiero is also throwing a code 45, rich exhaust, and I'm wondering if the engine stalling and the code are correlated. My potential thoughts right now are that I need to clean/replace the O2 sensor, check for more vacuum leaks, and potentially mess with the IAC..? Problem is- I'm totally new to this kind of stuff and I have no idea where to look for the IAC. If anybody has any suggestions on how to fix the stalling idle please let me know!

Hi! Best bet if you're getting a code 45, is to just replace the O2 sensor. They're fairly inexpensive. Get something like a BOSCH or a DELCO-REMY / AC DELCO / DELPHI.


As for the IAC, it's under the air cleaner, attached to the TBI unit. It has a 4-pronged connector on it, and it needs to be specific to your year. Sometimes people replace them from a different engine or GM car, or even forget to re-install the spacer, and then the Idle Air Control valve cannot properly adjust the idle air... so you get what you're getting now... almost stalling.


Let me search for a picture and I'll edit / update this post.


EDIT: Ok, I'm having trouble finding what I'm looking for... but this is your TBI unit (which is located under the air cleaner):



(Note: these are not my hands, not my TBI unit... I just pulled this off of eBay)


There is a sensor / actuator (as you know) called the Idle Air Control valve. It looks like this (Rock Auto): https://www.rockauto.com/en...rol+(iac)+valve,6072



Looks like there are two torx screws that hold it down, and it should just slide out.

[This message has been edited by 82-T/A [At Work] (edited 09-17-2024).]

The IAC controls air through a passageway in the throttle body. The IAC itself could be working perfectly (moving in and out as it should), but if the passageway is blocked with crud, then the required amount of air will not be able to make its way through. Sometimes all that's required is unscrewing the IAC and using a Q-tip to clean the area where the tip of the IAC does its thing. Use the Search function to find multiple writeups on doing this.