I've found a couple of topics on here related to hunting at idle, but no-one seemed to have the same symptoms I have, so I thought I'd post up looking for ideas.


My setup:

Stock '730 ECM
GMPP 350 HO crate motor
Holley Stealth Ram
Kirban adjustable FPR set at 50 psi


The issue:

My car will idle fine when cold, but once it starts to warm up (And enter closed loop), the idle will start to hunt up and down about 100 RPMs, occasionally starting to stall and recovering, with an occasional stall. This will occur in park or drive.

The car has no issues restarting, and will idle fine for a minute on restart before the hunting starts again.

I've checked the TPS, IAC, timing, CTS, etc and seem to be fine.

On a hunch I disconnected the o2 sensor, which smooths out the idle even when warm.

Thinking the o2 sensor was bad, I replaced it with a new one today. This didn't help, as the car still wants to hunt when warm.


Any ideas for where to go from here?

 

Next time it starts hunting disconnect the IAC connection. If it then runs smooth that is your problem. My car does the same thing but doesn't die and it is the IAC. But it sounds cool, like a top fueler at idle so I leave it alone.

 

Well, that's the thing. I'll try the IAC again, but the last time I did check it that didn't affect the idle at all, while disconnecting the o2 sensor does affect the idle (It smooths out).

This is with the old o2 sensor and the new one I just picked up.

 

did you test your injectors?

how about ignition do you have good spark and timing?

if it smooths out disconnecting the O2 then you are just telling the engine to go back to open loop. so it is not reading O2 anymore ergo, not impacting injector pulse and timing.

 

loosen your distributor and with the engine running and the est wire CONNECTED move the distributor back and forth and see if it will run better. The reason I say to do this is because the mark on the balancer can actually move and make you time it way off. just try it you got nothin to lose