2004 Jeep Grand Cherokee 4.0 acts like it jumped time
Asked by Garrett Jan 11, 2019 at 10:06 AM about the 2004 Jeep Grand Cherokee Columbia Edition 4WD
Question type: Maintenance & Repair
Hi, I have an 04 grand cherokee 4x4 With the 4.0 liter 6 cylinder and
automatic, 203,000 miles, I just bought it. The guy I bought it from said he
was driving it, it was losing power, and he eventually just shut it off and let it
sit. I put a battery in it and cranked it over, It acted like it wanted to fire but it
didn't start, and backfired. I checked trouble codes and nothing came up. I
sprayed starting fluid in the throttle body and no change
7 Answers
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Hornet_2497 answered 5 years ago
With that many miles, I too would suspect the timing chain jumped timing. With no codes it's hard to say. Starter fluid test indicates that fuel delivery is not the problem. A common ignition failure of this engine is the crankshaft position sensor, code P0320. It's located midway up on the bell housing, driver's side. They will sometimes cool off and start running again, but when they fail, there will be no spark for a while.
Thank You. I think it had no codes because the battery was out for so long and I didnt crank it long enough to give a code. I'll try that later today and see what I find out. If I still can't get it to throw a code, I'll change the crank sensor like you said, and I've also heard of a cam sensor causing this, so I'll change that too, they're only about 15 bucks a piece for cheap brand ones. I've changed them on other Jeeps before, but they just simply did not fire at all. I've heard that on these 4.0 straight 6's, they have a timing chain and they hardly ever break or wear out, and it looks like a bear to change
Hornet_2497 answered 5 years ago
You are correct about the codes were lost while battery was out. I might add, when a crankshaft position sensor starts to fail, the driver will notice that the tachometer hand will drop to zero suddenly and then bounce back up. That's because that sensor provides signal for the tachometer reading. Camshaft sensor is a lot easier to replace and it too provides spark and maybe injector signal. Good Luck
I did notice the tach doing that, but I figured it was because the battery was extremely low.
Hornet_2497 answered 5 years ago
Tachometer needle dropping suddenly and bouncing back up is a sure sign the crank shaft position sensor is cutting off spark and signal to the tachometer. I "counts" the rotation of the flywheel....RPMs.