Any idea on why? The idle either drops real low and comes back up or it drops so low the motor dies. It doesn't do it every time, its very random. If I do not hold the brake down all the way it seems to help. Is this low vacuum or something?

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1992 Formula 350
-SLP 1 3/4 Headers
-Ported Plenum, Polished w/ polished runners
-Airfoil and other small bolt on mods

 

Could be an issue with the IAC sticking closed (extended), or possibly too much gunk in the TB and it's passages.

 

have you checked for vaccum leaks?thhe idlee is set lower when in gear which means less vaccum and could cause it to die when putting it into gear.but i would say if it's a vaccum leak like that you'd notice it.it would ave to be a large port(like the brake booster line to the plenum)or like the other guy said the iac could be malfunctioning.....................

 

I would take your IAC out and clean it up, as well as the IAC passage.

Check for vacuum leaks by spraying TB cleaner by all the vacuum lines and intake gaskets.. listen for an RPM change.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Did you ever find out what the problem was? I am having similar problems and I am still working on it.

 

I as well have the same problem. I however have no idea what a IAC is??

Jesse

 

IAC is the Idle Air Control valve. Your problem does sound like either a vacuum leak, a clogged IAC passage, or the minimum idle needs to be reset. There's a couple tech articles on how to reset the minimum idle.

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Greg Westphal
'87 IROC 355TPI/A4

 

I should be able to replace my iac this weekend so if it helps I will let you know. The iac has alot to do with the idle so I'm going there first, and then I'm checking my distributer and wires and timing, and finally My injectors, Then if no avail I will have to keep searching. I will let you know what it was maybe it'll help you too, I know the feeling of having this awsome car and can't enjoy to its fullest.