Back in November I bought a 99 Wrangler 6cyl Auto and it was running great. Going from Albany and Syracuse a few times just fine. Sometimes though if it was cold the engine would act a little weird and run erratically; the tachometer would jump by itself without me doing anything. but if I let it sit and warm up it'd work it self out.
Fast forward to mid December when I'm heading back home to Albany from Syracuse when shit hits the fan. The engine revs erratically, it backfires and letting it warm up and restarting the engine does nothing. I manage to get it home and after an hour of the engine running bad like that the CEL comes on.
I didn't have the time to work on it myself so I drop it off at my local garage. They tell me it's problem code P1391 which comes up as a Camshaft Sensor problem. They go ahead and fix it, but a couple days after that it all happens again. They say it could also be the Crankshaft Sensor so I have them replace that too. This time it only lasts till the next day. They say they're not sure at this point, but it could be the ECM and they quote me $2000 to replace it. I bring the car home and replace it myself for $300. Runs fine at first then once I rev the engine to about 3000 it all goes back to the same with the same trouble code.
I bring it back to the garage and tell them to do what they have to and just find out what is wrong and fix it. Around that time I had to go back to school so I left it there for them to work on. They do diagnostics and call specialists and such. They end up finding a broken line in the wiring and patching it doesn't work so I buy a used engine wiring harness online and send it to them. They replace it and all the problems go away! My parents drive it for a couple days to test it then bring it to me in Syracuse. It runs fine for 2 weeks there and then I go home for a visit and it makes it fine.
Then once again shit hits the fan and on my way back to Syracuse it all happens again, the back firing and the erratic revving. I get it to stop doing it a few times by stopping the car, but it comes back after a few minutes of driving(even if I kept the rpms low, no higher than 2300). I manage to get it back to Syracuse and I find 2 trouble codes this time P0340 and P1391.
Symptoms: Engine revving erratically-intermittent
Happens when it's cold out more, but not exclusively then
Codes: P0340 and P1391
Already done: Crankshaft Sensor replaced-new part
Camshaft Sensor replaced-new part
Engine wiring harness replaced-used part
ECM replaced-refurb part
I will happily answer any questions you guys have. I'm just getting very very frustrated with this. Thanks for any help you can give.