91GTABird

Everytime i burn a new prom i get the same idle problems.

#1-About every 8-12 seconds while idleing the rpms with just drop and ramp right back up to target idle. I mean i can hum a tune to it b/c its so consistent.

#2-At all temps (worst when cold) my IAC is steadily hissing. Its can be 190* op. temp and at part throttle the IAC opens/hisses in sync with the RPM's. Same for idleing.

This is for every tune. I have started from scratch several times with a AWFY bbc and not even touching a thing it will do it. When use my stock prom and memal (AWFY also) it doesnt do it anymore.

I have read Blue86Iroc's "Idle Issues" 10x fold and still cant come to a solution.

This is a $8D LB9 mostley stock except for whats in my SIG and flows.

Thanks, Brian

Teeleton

If you move the idle adjustment screw to close the throttle blade, the IAC will open more, and if you open the blade, the IAC should close. If you want, you can make some small adjustments letting the computer react to set the idle position of the IAC so it's not hissing so much.

Teeleton

Grumpy

**Ported & Siamesed Plenum**

I wonder if it's enough that sometimes, the cylinders are robbing each other and you get an ocassional lean miss...

If changing the fuel doesn't cure it, then try timing, if that doesn't work move both of them around. There should be a cure tune wise, if not then it would seem to be there is a mechanical problem.

Hmm, BTW, does it puff any blue smoke at start-up?. A leaky intake seal, and a drop of oil getting into one cylinder can cause an odd idle.

3.8TransAM

I'm almost willing to lay claim on the valve stem seals like Grumpy said.(assuming its not still fitted with stock injectors)

My GTA is a stocker low mileage car.

Always had a little tick at idle that got worse over time.(not dependent on intakes, injector or tunes)

I'd lay money on if u threw plugs in it, it will idling almost glass smooth for a day or two and than do the same thing again.

Had ported intakes and plenums on the Formula in stock configuration as well and it never changed the idle for one way or the other even thru datalogs.

Might want to investigate that and see what u can find, pull the plugs and take a look, you will prolly find them in decent shape with the exception of a lite sooty coating from oil.

Also just swapped a ported stock intake and plenum onto my GTA to reseal the intake that had started seeping. It improved it, but again I know the valve stem seals are bad and every other day or so it will blow blue smoke out.

Just waiting for some extra $$$$ before I change my valve stem seals out.

later
Jeremy

91GTABird

I should have never asked. Yall hit everything exactley on the head and told me just what i didnt want to here

Really though thanks for the help.

Like a diesel.

Same here. Its getting worse though.

I changed the plugs about 2 months ago and they looked like they came out of an ashtray. I know the motor has excessive blowby and it is a 160K mile motor. I was just still using it as my test mule until my 355ci gets finished.

Thanks for the quick, accurate replys guys