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Discussion Starter · #1 ·
I have a 2002 Sahara automatic with the 6.... turn the key and it starts right up but experiences a rough idle for about a minute or so when cold. after that it runs and idles great. not a big deal but just irritating.

I changed the plugs (gap is set) but that had no effect.

The jeep has 103,000 miles on it. Engine and intake is all stock with no other issues, runs at the right temp with good oil pressure.

I'm new to jeeps but not new to working on cars, was hoping for a little insight before i just start throwing parts and sensors at it.

Thanks!
 

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If the problem only occurs at idle when you're not stepping on the gas, I'd suspect a dirty IAC (idle air controller) which is what provides all of the engine's air at idle. Cleaning the IAC normally cures that issue which is easily done using an aerosol throttle body cleaner. You can first try cleaning the inside of the throttle body with the cleaner by starting the engine and spraying the cleaner into the throttle body while keeping the RPMs up a tad with the throttle lever. The more you can keep the engine at or near idle the more the IAC will suck the cleaner in since it only draws air in at idle.

Removing the IAC shown in the second photo below to more thoroughly (but gently) clean its plunger and the oriface in the TB it fits into would be the next step, it is only held to the throttle body with two small torx screws.

If cleaning the IAC doesn't take care of the problem, I'd next suspect the TPS (throttle position sensor) is dirty inside and needs to be replaced. Unlike the IAC that can be cleaned to restore back to normal operation, the TPS needs to be replaced if it goes bad.
 

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Discussion Starter · #3 ·
Thanks Jerry.... I'll try both and see how it does in the morning. if that doesn't work ill get the TPS
 

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I think it's good to the check those things just as preventive maint but drought that to be the problem as the symptom would not stop when warm. Replace your upstream O2 (the heated one ) and you will probably fix your issue. Also if you smell your exhaust and it's pig rich that's a good indication that your fueling up.
 

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I think it's good to the check those things just as preventive maint but drought that to be the problem as the symptom would not stop when warm. Replace your upstream O2 (the heated one ) and you will probably fix your issue. Also if you smell your exhaust and it's pig rich that's a good indication that your fueling up.
I had this problem a few years back and it was my upstream 02 sensor also.
 

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Discussion Starter · #6 ·
Used cleaner in the intake... pulled the IAC and cleaned the shaft and plunger.... Cleaned the IAC orifice as best I could.

Started up cold this morning, no more rough idle and it seemed to sit at a higher start up idle (1000rpm) a little longer then it did before with it gradually coming down as it warmed up, which i believe is the way it should work.

I'll probably change the o2 sensor in the near future as preventative maintenance.

Thanks for all the insight! this forum has really been a time saver with all the things that I have done so far since buying it.
 
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