Okay guys, I promise I read threads before I start this one.....But I am still confused.....
2002 GC wj I6, 4.0, just turned into 140,000miles.
There used to be a poor acceleration and stall at idle issue 3 months ago, it got fixed by clean the Throttle Body, butterfly valve IAC motor cause they were really really dirty.
Things were going alright, except very occasionally, the idle speed would drop less than 100rpm if I stop with transmission selected to D.
Yesterday I got stall at idle again, along with hesitate to accelerate again, there was no code. So I checked the TB, everything attached to it is clean, but I still clean it with TB cleaner. After I put everything back up, I got a check engine light, and when the engine warmed up, the rpm drop to zero and stall out without TPS trying to rescue it.
I read the code in the morning, and the code is TPS voltage not agree with MAP sensor and the TPS voltage is right. In the morning the jeep has no problem(maybe due to the reason I did not drive it too far). I thought the problem is due to MAP sensor, judging on my TPS was from duralast, I got a new TPS and MAP sensor from Mopar and got them installed. Things were perfect, no more stall and acceleration issue.
But after 3-4 hours, when I tried to go home, the idle rpm drop to 300-400 rpm again, along with the occasional hesitate to accelerate. I park the jeep on the drive way, keep the transmission in D and step on the brake, the rpm drops to 3-400rpm and got rescued by TPS, and then it dropped again, the rps struggled a while at 3-400rpm, then stalled.......
What problem dose this looks to you? Jeep experts in the forum? It seems TPS and MAP sensor was not broken at all. My mechanic told me if the camshaft sensor is bad, I can not even start it.
What I should do? I saw people in the forum also check fuel pump, a few of them did the PCM swap, and I also saw this:
"well turns out I had replaced a crank sensor and vehicle speed sensor for nothing
after bringing it to the dealer eventually thinking it was the SKIM module and needing them to use their DRB scan tool to check,
the mechanic found the main wiring harness that runs from the PCM around the top back side of the engine (inline-6 4.0L) to the injector rail, had been sitting on the rear driver side valve cover stud and after 7 years/50k miles the vibration had allowed the stud to poke into the harness and short to ground three wires. That's what was causing the entire problem. At first the stalling out seemed random, then prior to bringing it to the dealer it would die within 3 minutes of starting it up.
During the diagnostic at the dealer, it died on them just like it had on me, they tried scanning the computer but found when it was dying that the computer was also being reset so no codes were being stored. And the way the mechanic explained that it was a short in the harness gave me the impression they've seen this before. It should be a TSB, because it was the way the jeep was built at the factory and is a definite problem, it will happen to everyone I think eventually if the wiring harness it tight around the valve cover and is touching on the valve cover studs.
After repairing the 3 wires, the harness was taped up and a piece of 1/4" rubber fuel hose was placed over the protruding driver's side rear valve cover stud so it doesn't wear through again.
I recommend anyone with the 4.0L inline-6 check the wiring harness running around the back of the engine and make sure it's not sitting on anything that can wear into it.
Could this be a reason for my jeep's condition, I did not get random stall, it stalls only when it stops.....
Thanks in advance!