I just ran my car for codes and only get 12......Driving down the road the car runs between 130*-160*.....when at idle at stoplight the temp will go upwards of 220* and it has actually gone up as much as 235*-245* so I installed a manual fan switch for my pass side fan and I turn it on when I am in stop and go traffic so the car doesn't get over about 160*.....I plan to change the thermostat out for a 180* (supposedly it still has the stock 195*).

I changed out the O2 sensor(a pita btw ) and Cap and Rotor. The problem is in drive idleing the rpm keeps jumping from 500-650rpm constantly, smooth for a few seconds and then iratic over again. I sat in my driveway and reved the car up and held it at different rpms and it did the same thing! There has got to be something wrong with my car, it does the same crap in park idleing. What to do?

 

check fuel pressure? possible wire arcing. wait until dark. start car and open hood. look for arcing around the plug wires.

 

Mike,

Aside from vacuum leaks, the FIRST thing I would do for an unstable or wavering idle speed is to clean the throttle body and IAC passages, check and set TPS voltage, set minimum air position, clean the IAC itself if necessary, and THEN bother with fuel pressure testing.

Adequate fuel pressure is very important as mrr23 advised, but is a little less of an issue at idle (unless it is WAY off, of course). If the fuel pressure were that much of a problem, you probably wouldn't be able to rev the engine as you have stated, and there would likely be other driveability issues.

Other than the O² sensor and cap/rotor, what else have you checked? Plugs, wires, PCV valve, air filter, all vacuum hoses, gasket leaks, etc. should be checked before you tear into any major components. Just my thoughts.

 

Does it surge or buck driving down the road? I'd check for vacuum leaks, clean the T-body like Vader said and check you're bleed air rate to make sure it's correct.

 

My AutoXray shows 0 IAC counts at idle and my TPS voltage is too high and my car does the same as yours but only when it's extremely cold. After it warms up the idle smooths out. Check for vaccuum leaks first.

 

Have you checked the MAF?
My car did some of the same except for the temps where not a issue. No codes nothing on the scanner.
Disconnect the MAF it will set a code. But if the car smooves out it means the MAF is sending bad info to the comp. If not it's what they said it might be.

 

it does sound to me, if i were asked to throw in what comes to ?mind? first, like its secondary ignition diagnosis time. and heres what you can try. getcher self a plastic squirt bottle like 409 or fantastik or one of the various household cleaners that are familiar to many women. hehee fill it with water and go pop the hood on your unsmooth beastie. start it up and let it idle.pick a bank, odds/evens either side-start lightly watering the plug wires down by the plugs\where they touch one another\around the looms\at the cap\at the coil-betcha watering the coil got you a biggie misfire, maybe even killed the motor. no? ok do same thing on bank thats remaining. are any changes in the operation of the motor? let me know but i dont think my input will be required for you to see whats up. can you also verify condition of-1) the ignition rotor 2)carbon button 3) is the coil in cap?i cant see the sig.here where im posting for your cars year-but model year isnt always the best guide.people seem to like that small distributor and remote coil better than its big bro.pull off coil wire-engine off-and check inside the ends for the whiteish oxidation powdery stuff that messes with you. ck.coil tower and cap towers where plug leads attach too for same stuff, is rotor center burned black?give the pickup an eyeball and check for frayed insulation cracked magnets, etc-let me know how it goes-later

 

I have had a couple probs like that. The first time it was the small timing module in the distributor and the second time it was a bad TPS. The TPS was a bitch to Diagnose because mine is the non adjustable type. I found it by fluke actually. Instead of reving the motor I push it the oposite way and it came out of it. Other thing you might check for is the EGR mightnot be seating well and like they already said, Get some GM "CLEENS" from the dealer (it is cheap) and clean out the gunk in the IAC. I have put 2 in already.

 

there are reasons for most anything some we can figure, some we cant-a reason iac motors go south is because someone made a bad adjustment or a supporting component elsewhere in the system failed-but for sure, no matter what the reason is-an iac count of 0 will get you a failed iac valve over time-sometimes a short period sometimes a bit longer. same if the counts are maxed on the open side. repeated failures of a replacement part is an indication that a more complete diagnosis is in order. its like this-replacing the bad part is only repairing the SYMPTOM of the problem-the way the problem is showing itself, the underlying CAUSE of the obvious part failure has got to be discovered. hence-parts changers-----------------------diagnosticians who change parts. :lala:

 

Well today I got the thermostat swaped for a 180* and the throttlebody was pretty nasty The guy that did the work (I didn't have the tools, all friends at work ) cleaned the throttlebody out and either set the timing or the iac and it runs better now, there is a slight pulsation of the rpm at idle but it is 75% better now than what it was.....I also went down to the exhaust shop and got rid of my cat. converter with a strait pipe.....Boy....she sure does run better, normal wise and power/response wise