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Discussion Starter · #1 ·
I drive an '02, 4.0 with the auto transmission. Lately the Jeep has been trying to stall when I first start to drive. For example, every morning before work I start my Jeep for about 5 minutes. When I back out of my driveway and start to accelerate the Jeep will stutter and try to stall. After a second or so it will drive fine. When I leave work (8.5 hours later) the Jeep will accelerate fine until I come to a stop, then it will start to stutter really bad until I give it gas and then it will drive fine. I don't warm the engine up before leaving work.

I have tried cleaning the IAC, throttle body (Was covered in carbon buildup), and changing the spark plugs (Autolite APP985) but the Jeep still acts up. Could this be related to the TPS or even the CPS? I'd prefer to get some opinions before throwing money on anything else.

Thanks in advance!
 

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Is it idling at the correct RPM?
Vacuum leaks?

My other car did this an it was a bad IAC. It was intermittent and sometime it wouldn't throw a code for 100 miles.
 

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Discussion Starter · #3 ·
Is it idling at the correct RPM?
Vacuum leaks?

My other car did this an it was a bad IAC. It was intermittent and sometime it wouldn't throw a code for 100 miles.
It idles at about 400-500 RPM when warm. It's been acting like this since November and I haven't gotten any codes about it. I can check for vacuum leaks this weekend.
 

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400-500rpm at idle seems pretty low to me. I could be wrong. My tj idles more like 700-800. Though we do have different engine's and mines manual
 

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Carl brock

Believe it or not, bought my jeep about 4 months ago its a 2002 4.0 auto. And was doing same as yours. I read somewhere that a weak battery could cause this, sounds crazy, but bought a new one and it runs great.
 

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Discussion Starter · #7 ·
Believe it or not, bought my jeep about 4 months ago its a 2002 4.0 auto. And was doing same as yours. I read somewhere that a weak battery could cause this, sounds crazy, but bought a new one and it runs great.
This actually seems like it could be the issue. Every morning when I leave for work it's dark outside. When I start to give it gas and the engine starts to stutter/try to stall I notice the headlights start to dim.

Does this sound like a battery issue?
 

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try disconnecting the upstream o2 sensor and see how it runs. Mine kinda acted that way, turned out the heater element in the sensor wasn't heating the sensor up. When it went into closed loop operation the bad sensor caused a bad fuel/air mix, which made it run real rough...
 
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