Oscillating idle on 3.2L
 

I've searched the archives because I thought I've seen this problem come up before but I haven't been able to find a solution. Anyway, once my 3.2L gets warmed up and only at idle, the engine rpm's oscillate between ~900rpm and 1200rpm. When the engine is cold, it idles fine. what should I be checking??? O2 sensor, idle valve, idle adjustment??? Thanks for any suggestions

Mike

O₂ sensor would be my 1^st guess

I got a similar symptom to that troubleshooting my flywheel reference sensor problem. I plugged in a new head temperature sensor to the connector but it wasn't installed in the cylinder head, just laying down by the valve cover. And the idle hunted like the idle control valve was bad. Do you have the two wire HTS? It's easy to check it with an ohmmeter. But Bill's probably right. How many miles does your 02 sensor have on it? Another thing you might want to do is take the idle control valve off and squirt it out with some carb. cleaner, could be just gummed up and sticking.

My .02
jw

Don't listen to these guys. 3.2 came with factory oil leak and ***** for an idle. It's part of life.
Put in Techron. That will clear it up. Unless you got something wet, that's the problem.
If you have K&N, techron will definitely cure it.
DME's idle like complete *****. One effing thing goes wrong, they go up and down like 70s porn film.

I already played the O2, idle stabilizer valve, bla bla bla game, so let me save you some money: techron.

The conventional wisdom says O2 sensor. They should be replaced every 60,000 (80,000?) miles. Techron couldn't hurt.

Thanks for the suggestions. I've cleaned out the idle valve, the engine has a new flywheel sensor but I havn't checked the head temp sensor yet. I've run techron through the engine. The O2 sensor is a three wire and it probably has about 20,000 miles on it if that. I did have to pull it out when I removed the exhaust from the car though. Could it have been messed up while it was hanging in the wheel well while I had the exhaust off??

Thanks
Mike

Had the same thing on my 3.2. Was the idle control valve. Switched it out and the idle is steady at 900 rpms for the last 3 years. Several other guys here have had the same thing. Find another 3.2 and switch the valve out (takes 10 minutes) from another car to confirm before buying as they are $120+.

O2 sensor does go bad after a while and its not a bad idea to change it out after 70-80k miles.

Joe

Is it possible you got some anti-sieze compound on the sensor when you replaced it?

Try the Techron. If that doesn't work, try a new O2 sensor. Head temp sensor could also be the culprit. I hear they're a PITA to take out. If you're going to go through the trouble of taking it out, you might as well just replace it and have some peace of mind. They're not that expensive.

Good luck.

On my 88 the same symptons were eliminated by new O2 sensor which I replaced at Early S Man's suggestion. Idle stable as a rock ever since.

Also, suggest you adjust the idle control as outlined in Bentley's. John Walker also briefly describes it here:

http://forums.pelicanparts.com/showthread.php?s=&threadid=8880&highlight=idle+adj ustment

My 3.2 has a rock solid idle.

Forget the 02 sensor...if you unplugged it, chances are that it would still be ocillating at idle. Did you try that?

Instead, reduce your idle speed at the idle air bypass screw on the throttle. That should take care of it!

Cheers,

Joe