I am having idle problems with my 94 z. I drove the car to work one morning, and the car did not move again until i left work again 8-9 hours later. When I turned the car on, the car started to idle from 1000 to 2000 rpm eradically. So I drove the car anyway. Whenever I got the rpm close to 3000, the car started to almost misfire or hesitate. After about 1-3 minutes of driving, the car stopped the rough idle and ran perfect. This seems to be the way the car runs lately. If the car sits overnight, it runs fine the next morning. If I am in an out of the car, every time I turn the car back on i get the rough idle for a minute ot two and then it stops. Does anyone have any ides? I do not have any scan tools, so i need a good guess, or somewhere to start. Any help would be greatly appreciated.

Car Info: 1994 Camaro Z28 w/ 6 speed
Miles: 59,000
Mods: Mac Headers w/ Y-pipe
Gutted Cat
Magnaflow cat back
160 thermostat

 

If the SES light came on get it scanned. Until then you can check a few things. Pull the vac line off the FPR and see if its wet with fuel. If it is, replace the FPR. Take off the EGR and see if it's sticking. Clean it and reinstall it. Clean the IAC and reinstall it. Clean the throttle body and reinstall. Check all the plug wires for bad spots, and all wires to the opti and coil as well. Consider doing a good tune up if you havent done one in long while. Have the injectors professionally cleaned.

 

I have had this same problem with my 94 z. It basically revs up at idle when I come to a stop light to about 1000-1200 rpms. It only seems to do it in warm weather and when the car is warmed up. I have cleaned the intake with carb spray, ran some fuel injector/ gas treatment bottles in the fuel tank. It seemed to help out a little. That was last summer. Now it is doing it still this summer but not quite as much. I believe it may be a dirty or clogged EGR valve (Exhaust Gas Recirculation - I think is what it stands for). I was doing some reasearch last summer and that seemed to maybe be the answer. I have been stumped because I ran a scan tool, no codes, took it to the dealer, all they said was carbon build up basically. No IAC valve that is bad (Idle Air Control) valve which I thought could be the answer. Pretty much I am to the point where I am going to try and remove the EGR Valve depending on how hard it will be and check that out, maybe replace it or clean it. If you get any more info or anybody else has seemed to find the answer to this I would like to know.

P.S. Some people may say ignition opti spark or whatever, I have had spark plugs, cap, rotor, wires all that replaced recently. I am almost positive that is not it.

 

Cleaned the EGR Valve today. Was pretty built up with carbon, I believe it was still working properly so I just cleaned and replaced it. I wanted to have a new one to compare it with, but $78 at the dealership and he had to order it. I thought maybe it may have not been closing all of the way. Anyway drove it today and no reving while idling. And it was hot today. Got up to about 220 degrees engine temp and didn't do it. That's usually when it happens. I think it may be the EGR not closing all the way that is causing those problems. More that I think about it, it did it the worst after I got off the highway for like a 30 mile drive, which during then I'm running 2000 RPM or so the whole time which is when the valve is supposed to be open I believe. Then I back down to idle when I stop and it may not be closing completely, from the buildup. So it makes sense that that would be causing that kind of problem, if that's what you are having. Hopefully it stays working well and I may have solved this ongoing head ache of a problem.