2001 jeep grand Cherokee straight six. My problems started out with what would seem to be a rough idle. Then gradually got to the point that when I was driving it almost seemed like the ignition was turned off; i.e. would be driving 45 mph and all power would be lost, power steering, brakes, unresponsive guages. I could throw it in neutral, tap the gas and get going down the road again. Its favoriate time to do this was in the middle of turns. Then from there it started dying after I started it unless I toggled and played with the gas at idle and anytime the rpms got below 600. Codes thrown: first was a third cylinder misfire. Then it was saying that the timing chain jumped one or more teeth, then followed by a camshaft position sensor, then put up a crankshsft position sensor. I since replaced both sensors and cleaned the IAC valve and throttle body. I have a leaking valve cover and have had some oil pressure issues once before that seemed to solve itself, although I think it still may exist because of the great variance of oil pressure when driving and not driving. Anyone have any ideas without me just throwing parts at it or taking it to the dealer? I'm out of options and time.

 

Check the fuel pressure. A leaking valve cover won't effect the oil pressure, it just makes a mess.

 

I agree I say you have a fuel probblem

 

Ok, sounds like an idea, how do I go about checking fuel pressure and what could be a problem?

 

You can buy or rent a fuel pressure gauge the screws onto the test port on the fuel rail, then turn the key to the run position. The needle on the gauge should go up to between 40-50 psi (not sure of the actual spec). The pressure should not drop right away when you turn the key off. Start the engine and watch the gauge, it should read steady and not have a bouncing needle. A clogged strainer at the bottom of the pump could cause low pressure as could a worn fuel pump. The gas we use today is kind of hard on fuel pumps.

 

for future reference, a leaking valve cover gasket can also cause some oil to get into one of your sensor connections also. especially the oil pressure sending unit (switch).

 

Next time you replace the valve cover gasket, clean out the oil drains. Oil should not be accumulating above the gasket and causing the leak.

 

Ok guys, update. Fuel pressure was fine, read between 45-50. Ugh this thing is wearing my patience thin

 

Check the big wire harness that runs along the back of the motor on the firewall. If it's chaffed through and covered in oil, it's a good place to start. That wire harness sends all your intake sensor reading to the PCM.

 

I have an 01 4.0 started trying to die at idle, then became worse and died at 40-45 mph when letting off the gas ( coasting so to speak), tack goes to zero but all electrical stuff still on. Gave a little gas and took off again. This problem was very intermittent. Then got to where it would die, had to pull over wait a minute and restart. Got to where it didn't want to restart. Codes read all kinds of stuff. So I replaced the computer, because my 96 had a bad computer, even though the problem wasn't supposed to exsist with the 01's. Check engine light came back on and read different codes all together... read evap purge selonoid and 02 sensor. Replaced 02 sensor and check lines to evap, had a loose cracked vaccum line to evap. Not dying anymore, still has light on. We will see? Any suggestions besides going ahead and replacing selonoid?