Help i have a 1999 Grand with 4.0 I keep getting a PO340 code and I have replaced the cam sensor and the drive and syncronized the sensor reset the cam crank corelation still after you drive 20 miles or so the check engine light comes on and 340 is back sometimes the jeep bogs down and you have to shut the switch off and restart it and it runs like new any ideas?

 

It could be a PCM problem or a mechanical problem, the hard part id figuring out which one it might be. Google the trouble code and follow the trouble tree very carefully, you may find something. A worn and slack timing chain might cause that code, as can a broken flexplate. But the fact it starts acting up after 20 minutes makes me think it might be a heat related problem with the PCM.

 

the engine was rebuilt about 5000 miles ago so timing chain is new the crank sensor is new and also the cam sensor

 

I guess I will try an ecu I usually dont like to just throw parts at a problem but in this case im at the end of my rope lol