I have a 1998 Z-28. Last summer, I added a GM Hot Cam, Edelbrock heads, a FAST 92 intake manifold and throttle body along with SLP headers. I've had the car dyno tuned. But, it won't hold an idle and dies when coming to a stop. I've taken it back to the tuner twice. As soon as I get it home, it acts up again. I'd appreciate any advice on how to solve this idle problem, thanks.

 

Do you have access to a scanner or scanning software that will allow you to observe the PCM's control of the idle air control system? Sounds like it isn't responding.

The PCM typically elevates the engine idle speed when the vehicle is moving, and holds it there until the vehicle comes to a stop (VSS = 0). That is a programming feature. Then there's decel fuel cutoff, which generally is only used until the engine RPM drops low enough that the fuel is turned back on to keep the engine running. That is a programming feature.

But first, check the IAC motor and make sure it's working and the idle air passages are not plugged up.

 

I don't have a scanner. It looks like I'll have to make another trip back to the tuner. Thanks for your advice.