OK Guys..I'm stumped now. Just replaced the EGR Temp Sensor, EGR gasket,Intake Air sensor, MAF Sensor, New Plenum gaskets, TB gasket.ECM as well .Now it wants to hunt at Idle halfway warmed up. when it is warm it idles ok until it put it in gear then Idle drops down to 380 or so tries to stall then recovers to about 700. I disconnected the TPs Sensor to see what it was doing without it and its at 1300!..I cant get it to idle any slower than that even with the screw backed out on the TB, with TPS disconnected. Is this normal for this car to race like this without TPS hooked up? Other than that it runs OK. I've got steady 15 in vacuum..No jumpin around. Can anyone help?? PLEEZEE.
Heh if not you all may just see it for sale, because I just dont know what to do with it anymore. Thx Frank

 

It is normal for the engine to idle high without a TPS hooked up. default idle speed.
For the hunting idle. Pull the idle Air Control motor (IAC) located on the RH side of the TB (big round thing). Clean it throughly (I use Valvoline Syn power throttle body & carb cleaner), clean out the idle passages in the throttle body throughly as well. While holding the IAC body push firmly down on the pintle and rock it back and forth so it will retract all the way. Install the IAC with a new gasket and then proceed on to the minimum air adjustment followed by the TPS adjustment.
If after the cleaning and adjusting it still has problems...replace the IAC.

 

As stated, it sounds like the IAC. Very often, when the problem you're describing exists, a new IAC is the cure. I believe a new one is around $50.00

 

Hi.
I have an 85 4+3. I have had some idle problems. I did a lot of things to get it ok.
What I would do first is to clean the throttlebody thoroughly. That includes the IAC valve and also internal at the seating of the valve. There is a lot of carbon deposits in the throttlebody. Then check if the IAC valve works or if you can borrow one that works you can eliminat tthe IAC faults. I had a problem with vacuum leaks. Cjeck all the vacuum hoses and tubes. The ones under the plenum were brittle so I had to change all of them. The engine hunted again and I did the vacuum leakage test that will show the leakeag at the plenum or manifold. I sprayed some starting gas around the gaskets and found that the engine increased the revs when spraying over the manifold part where the runners are connected. I took of the runners changed the gaskets and ensure that there where no leakage by adding some silicon "gasket". After that cure everything were all right. In the process I checked the EGR valve and found that it did not hold the vacuum when I applied it to the vacuum input. I also changed that valve. I do not think it is working in idle mode. I also adjusted the min. idle air after the book and the TPS voltage to between .54V and .64V (my adjustment were 0.58V).
After that cure everthing became super. I think the main thing was carbo deposite and the vacummleaks.
Good luck

 

85's are designed to idle at 550 in drive way too low for my liking!
I had a custom chip burned. [not one out of a catalog]Get one with a 650 or 700 idle in drive and everything should be fine. The stock programing is bogus anyway its costs power definately will run better with a stage 2 custom burn. You need someone who can burn it for you.
85's are all by themself but you can find them on E-b-a-y.
Make sure you ask for and get the higher Idle or its a waste of time.

 

Did more checking today with a vacuum hose stuck in my ear, when I got down around the lower runners where they bolt onto the intake, It damn near sucked my eardrum out. Evidently its sucking air down there as evidenced by the rear gasket I took out of it.So out came the runner..I wanna meet the guy who designed that setup..Oh man 2 hours of misery but finally I got it out. Now I can't find anyone who has those lower gaskets...Uppers are easy to find but no lowers. Is this still a good GM part number(As in still available). I also really wanna put some copper RTV on those when I put it back together. I know everyone says its not necessary but I NEVER wanna take that apart again. Anyone got any Ideas?? Thx Frank

 

Your not alone with your car, my 89 is doing the same thing at idle now that you figured out the leak I am going to check mine as well, i hope that's my problem well good luck with your fix!

 

Hi.
Good that you found the leakage. I have no problems with getting the lower gaskets here in Norway so I would imagine that over there there it must be quite easy to get it. Have you tried Corvette Central or Mid America. It might take a day or two.
I think that cpper gaskets there would not be flexible enough. If you had problems with leakage there might be that the surface is uneven or chirped. I used new gaskets and in addition applied some silicone to ensure to have no leakage
Jan-Erik

 

There are complete TPI runner sets including TB gasket on eBay all the time for $11
Check out item #7996813161