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autopc25 01-09-2010 08:44 AM

Erratic idle after start up for a minute when hot or cold?
I have a 1997 Wrangler with 2.5L 4-Cylinder, auto trans, A/C.

The car will idle erratically a minute after start up when it is cold or hot. The idle will go up and down for a minute or two or until I press on the gas pedal and rev it a little. The car idles and runs fine after this? This happens every time after I start the car, it does not matter if it is cold or hot. On cold days the car fires right up and idles at about 1500 rpm to warm up then the rpms drop to idle at about 800-900 rpm. A minute or two after idling normally the idle will be erratic then go back to normal after I rev the engine for a 30 seconds or so? If I start driving right away the erratic idle will appear after the engine warms up and the the car will surge when I press on the gas, I have to rev it a few times then it runs smooth for the rest of the drive. The car will run perfectly until I turn off the car and restart it, even when the engine is still warm. The only difference is the engine will not need to warm up so the idle is at 800-900 rpm instead of 1500 rpm like when it is cold. A minute after start up the idle will idle rough for a minute or two or I have to rev the motor for 30 seconds then it runs fine?

It was doing this before and after this work. I recently had tune-up with all new parts and cleaned throttle body and idle air control motor with carb cleaner. A broken exhaust manifold bolt was replaced and the mechanic said the intake had a leak but he replaced the broken bolt, exhaust and intake gaskets. The car ran much better after the intake leak was fixed but the erratic idle is still a problem. I had a 2 different jeep mechanics look at it. One of the mechanics scanned it and found no codes thrown and the oxygen sensors seem to be all working? All work was done by a Jeep mechanic.

Both mechanics said the car should throw a code but it has not yet? I don't want to wait for a code to be thrown and get stuck on the side of the road.
Any ideas?

Jerry Bransford 01-09-2010 11:12 AM

Did you physically remove the IAC to clean it and clean the oriface (hole in the throttle body) the IAC's plunger fits into?

autopc25 01-09-2010 06:25 PM

I was there when the mechanic removed the IAC. He cleaned it with a soft cloth and wire brush, then he sprayed carb cleaner. He also cleaned the hole in the throttle body with a brush and cleaner. It looked pretty clean after he got done.

It's funny there are no codes thrown yet?


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