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Discussion Starter · #1 ·
I have a 2001 TJ with a 4.0 about 150K miles with the following recent work:
Valve job, new plugs, coil pack, injectors, IAC, MAP sensor, Cali model with all four o2 sensors replaced, new fuel pump, coolant temp sensor and TPS. Crankshaft position sensor is less than a year old.
Cats were replaced about 5 years ago, fuel pressure test is spot on, compression test passed with flying colors and he tested for and fixed one small vacuum leak..

This dang thing thing runs fine until it goes into closed loop. The guy I have working on this is beating his head against the wall, has had a specialty troubleshooter come in and he is at a loss as to what is going on too.

The o2 sensors are all reading within a percent of each other, and the fuel is (forgive me here because the nomenclature is escaping me but related to fuel trim) i.e. -25 when it is in closed loop. These readings were taken on a snap-on live data reading (two different ones actually).

Has anyone had any issues with this type of thing or if you have any suggestions on something he may be overlooking as he is at a loss? Stealership is only going to throw new parts over the ones I have already replaced.

One addition, he put a new computer in this thing and it did the same thing so he took it out and put the old computer back in since it wasn't the remedy.

I hope this is enough info, I can always ask for more technical info if needed. thanks in advance
 

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What brand of o2 sensors? TJs seem to be picky, and the only ones that worked in my jeep were NTK/NGK.
 

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I know it's a long shot, but mine always runs like crap when I use aftermarket ignition wires. Don't ask me why... it just does. I have tried several aftermarket wire brands, but the mopar ones are the only ones that don't make the engine stumble, especially in damp or rainy weather. It makes no sense to me, but it just is.
 

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Real long shot as all 4.0 TJ from 2000 on including his 2001 have no ignition wires instead a coil rail with 3 coils and six spark plug boots directly attached to the rail
 

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Discussion Starter · #9 ·
It runs normal until it goes in to open loop then it does the too rich thing in both banks, RPMs drop at idle and will cut off. If at stoplight I have to switch to neutral and watch the RPM's (not driving it at all right now b/c won't pass inspection)
 

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Camshaft Position Sensor is inexpensive, easy to replace, and worth a try. Also consider inspecting Camshaft Position Synchronizer.
 
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