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Unread 06-20-2010, 02:47 PM   #1
ljhopp
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Need Help Really Confused

99 wj 4.7
I keep getting a check engine light on for p1391, I have replaced both the cam and crank sensors. I have even replaced the tps to see if that would work but the jeep still puts out a check engine light. Along with the check engine light on the jeep is missing or studdering when I floor it. I am really confused to what could be causing the jeep to have this problem. The jeep will also sometimes not do it, so I floor it again and then it will do it again.

I also have just replaced this engine and I don't no how long the jeep was siting before I bought it so I don't know if the pcm has a problem, or if the pcm has the lastest flash. When I replaced different sensors the problem would happen at different rpm's when I floored it. I am lost to what the problem could be. Since every time I replace a sensor the jeep will run good then all of a sudden start having the problem again.

I am thinking maybe a bad pcm or a bad fuel filter but again I am just guessing.

Any help would be greatly appreciated.

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Unread 06-20-2010, 03:15 PM   #2
Wrangler11
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Maybe clogged injectors since it only seems to happen when you floor it... Stop flooring it.
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Unread 06-20-2010, 03:41 PM   #3
ljhopp
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Maybe clogged injectors since it only seems to happen when you floor it... Stop flooring it.
Would that cause a p1391 check engine light to come on.
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Unread 06-20-2010, 06:04 PM   #4
ljhopp
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Here is a link to the engine.

YouTube - 99 jeep grand cherokee with p1391
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Unread 06-20-2010, 06:46 PM   #5
ljhopp
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Does anybody have an idea?
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Unread 06-20-2010, 07:27 PM   #6
narnwv
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what's making the ticking noise when you're aiming at the engine bay? where is that coming from?
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Unread 06-20-2010, 07:30 PM   #7
ljhopp
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what's making the ticking noise when you're aiming at the engine bay? where is that coming from?
The ac compressor is where it sounds like it coming from.

The engine I just got as a reman.
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Unread 06-20-2010, 07:51 PM   #8
narnwv
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p1391 is "intermittent loss of cmp or ckp" I'd double check the connectors, make sure there's no corrosion, and follow the wires and make sure there's no kinks or sharp bends, etc.... I'd also check nearby grounds, pull them and sand off corrosion/rust.
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Unread 06-20-2010, 07:59 PM   #9
Wrangler11
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Originally Posted by ljhopp View Post
Would that cause a p1391 check engine light to come on.
No idea, just a guess based on what is happening.
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Unread 06-20-2010, 09:07 PM   #10
ljhopp
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Originally Posted by narnwv View Post
p1391 is "intermittent loss of cmp or ckp" I'd double check the connectors, make sure there's no corrosion, and follow the wires and make sure there's no kinks or sharp bends, etc.... I'd also check nearby grounds, pull them and sand off corrosion/rust.
I have a haynes manual, so I have all the codes and what they mean. I am just really confused to what is causeing this. I double checked all the connectors and they look good. I think their is short somewhere in the wiring because it seems like the more I drive the jeep it seems to start having the problem soon on the rpm's. At first it wouldn't do it when in park and reving it, now it does it when in park and reving it so it seems to be getting worse. But as soon has it gets past the studder it takes off like nothing is wrong.
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Unread 06-20-2010, 09:40 PM   #11
ljhopp
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Could the map sensor be causing this problem since it controls fuel delivery and lignition timing. Sounds like good guess to.
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Unread 06-20-2010, 11:06 PM   #12
ljhopp
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Quote:
Originally Posted by narnwv View Post
p1391 is "intermittent loss of cmp or ckp" I'd double check the connectors, make sure there's no corrosion, and follow the wires and make sure there's no kinks or sharp bends, etc.... I'd also check nearby grounds, pull them and sand off corrosion/rust.
Do you know where the wires that come from the sensor's go to? What pcm harness connector are they connected to, the one on the left side or middle or the right side.

Thanks
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Unread 06-21-2010, 09:44 AM   #13
narnwv
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I am unsure which connector they are. It's not going to hurt anything to pull and clean the battery terminals, but while they're disconnected--pull and inspect the PCM connectors.
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Unread 06-21-2010, 09:18 PM   #14
ljhopp
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I am unsure which connector they are. It's not going to hurt anything to pull and clean the battery terminals, but while they're disconnected--pull and inspect the PCM connectors.
I did all that today and still nothing I even checked all the volts and grounds at the sensors and everything checked ok. I think I have a bad pcm that is causing the problem.
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