Hey Everyone,

I just acquired an automatic 88 IROC with a 383, bigger cam (not sure the specs on it), Edelbrock TPI and MSD Ignition. AIR system deleted. Still has EGR but is capped off.

I've been trying to figure out this stalling/fluctuating idle issue. Google/forum search has helped me troubleshoot but hasn't gotten me quite there. The car will start up and idle just fine while in open loop. Once it seems like it goes into closed loop, the idle will fluctuate between 600-1200 RPM and the car will stall if put into gear. It'll idle and go into gear just fine if I disconnect the MAF.

What I've tried so far:

• Check and confirm no vacuum leaks
• Replace MAF
• Replace O2 Sensor
• Replace and relearn IAC
• Set TPS voltage, adjust idle screw
• Adjust timing
• Reconnect EGR

Any thoughts on this would be greatly appreciated.

 

Does the car have a custom tune for running the larger motor? And mods to the ECM? Or other electronics? Getting any codes from the ECM??

 

If it isn't tuned she'll act all sorts of weird with a 383 and bigger cam, that's for sure.

 

Thanks for the replies.

No idea if it's been tuned. If I had to wager a guess, I'd say probably not. It was throwing a few codes including the MAF and the O2 before I replaced them and reset the computer. Haven't driven it since. Anybody know of any tuning software or anything I can use to at least look at live data?

 

Tuner pro rt is a great program. If it hasn’t been tuned you are more than likely running $32B mask.
most update to $6e 89 mask with custom builds.

 

https://www.thirdgen.org/forums/diy-...-adx-mask.html

 

Please get a way to scan and read data. Need to see what is going on when the surge is hitting.

 

Check the ecm and see if theres a chip adapter in it or some type of aftermarket chip with any labels on it

 

Most of the online procedures for setting the minimal idle setting leave off disconnecting the timing connector to the distributor. To do it right, it must be unplugged while setting the minimal idle speed and TPS voltage. If not, you’ll get a roving or “hunting” idle.

If you did that, I'd double check all the engine grounds. If those checked OK, pop off the cover on the ECM and make sure the prom is properly set and not loose.