I drove home yesterday and noticed when I puled up to a stop sign the idle wasn't coming down like it normally does. It started out as an intermitent prob and now it won't come down off about 1500RPM's. Last year it did this and i ended up replacing the IAC and the timing module. My friends think it is something to do with the EGR but I think it is the IAC again.

I took the snorkel of the from and sparyed some GM CLEENS in the IAC passage and the motor hauled down and then came back. Afeter a couple of shot I gave a few sharp blasts of thottle and the idle came down to where it should be. I did this a couple of times as everytime I restarted it wouldn't come down of the screaming idle. Do you guys know anything that could help me?

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit
One sweet sounding system

 

Could be your TPS or maybe a vacuum leak.

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92 RS, 350, Street & Performance MPFI, TFS heads,
Crane Rollers,
MSD Digital 6 Plus, 22lb injectors,
ZZ3 cam, Edelbrock Headers 1 5/8, 3" Exhaust,
Hi Flow 3" Cat, stock T-5,
stock rear 3.08, koni yellow adjustable front, twin turbo glass hood, T-tops, Auto Meter Ultra Lite Series 2 5/8 gauges, Teal Green

 

I'd say vacuum leak. I'm still learning about the TPI, but my old MPFI was very similar, and there were a LOT of plastic hoses that got brittle and would break, and when the right ones did, it would cause high reving.

-Reno

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89 Formula

 

you probably already checked this, but the throttlebody might be sticking. when the car is racing at 1500 rpm at idle pop the hood and see if the throttle blades are returning to the closed position. my first BBk 58 TB did this. tried everything until i figured it out. just a thought.

 

If you tap on the throttle does it idle down? Also (with the engine off) check to see if the throttle arm moves back and forth. If it does this means you have a worn out throttle body.

 

Thanks for the help guys but I have already checked all that. I first thought a vacum leak but it will Idle down sometimes. If I plank on the gas hard it will sometimes come down.

I had to make an emergency run to the hospital this weekend so i had to take it. On the way home it started working again so I am not sure what it is. My EGR has not been working for sometime so I think I am going to fix that and take the IAC out and see if it is binding. I think the IAC may be over compensating for no EGR hooked up and It might be binding like the old one did. This is my best guess. I don't think it is a vac leak because it is intermittent

Any comments would be greatly appreciated!!

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91 Z28 Camaro
305 TPI
Flowmaster 3" exhaust
700R4 with 2000 Stall and shift kit
One sweet sounding system