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Old 09-01-2010, 11:43 AM   #1
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Lightbulb CMP vs CKP

Hey guys,

I have previously brought up my issue with my 2002 wrangler, 4.0, 5spd, 82k miles stalling backfiring sputtering and so on with no responses....

so after doing some more research i am finding a lot of people discussing the crankshaft positioning sensor and the camshaft positioning sensor. it seems to me alot of people get these confused. unless they are the same thing.
if anyone else has had this problem can you please shed some light on the locations of the sensors? maybe a pic or two would help.

CEL
P1391 Intermittent loss of CMP or CKP

and here is the original thread fyi

http://www.wranglerforum.com/f5/elec...ire-59824.html

thanks guys!

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Old 09-01-2010, 11:50 AM   #2
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The camshaft and crankshaft position sensors are two separate sensors.

The camshaft position sensor tells the engine where the cam shaft is so it can properly time the fuel injectors and spark. This sensor is located on the distributor shaft, on the passenger-side of the engine.

The crankshaft position sensor is what provides the engine's master timing signal. That sensor is bolted onto the transmission next to where the engine's flywheel is, up high on the driver's side. It generates timing pulses based on notches cut into the engine flywheel.

Either can cause similar symptoms... engine stalls, sputters, etc.. Possibly due to the crankshaft's more exposed position, it seems to fail slightly more often than the camshaft position sensor does.

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Old 09-01-2010, 12:32 PM   #3
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A problem area that seems to keep cropping up - those sensors are high impedance, a small amount of resistance in the connectors or wiring can cause the signals to reduce to the point of trouble.

A trick that sometimes works - simply unplug the connectors to them, then plug them back in.

I've at least temporarily cured a few "no start" or "stopped running" conditions by doing that (some by phone, some on the side of the road.) I have only tried it on the Crankshaft Position Sensor, but the Cam Position Sensor may also be suspect.

It's certainly worth a try.

Let us know if it helps the backfiring, sputtering etc.

You might try a small dab of Dielectric grease on the connector if it made a difference. Only use Dielectric grease, other types of grease may be too conductive or corrosive.
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Old 09-02-2010, 03:15 PM   #4
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thanks guys, i really appreciate the input.

hopefully the connections just have grit and grime on them.

i will keep yall posted
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Old 09-02-2010, 03:17 PM   #5
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Flushing the connectors out with WD-40 is a highly effective way to clean them if you don't have an actual spray electrical contact cleaner to use. Just shake the excess WD-40 out before reconnecting the connectors back together.
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Old 09-09-2010, 04:19 PM   #6
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Hey guys well here is the update... I got off of work this morning and the jeep turned over and started . It ran for 30 sec before sputtering and stalling. It will not restart. I went to autozone and picked up a crank shaft positioning sensor and installed it.
It still will not restart. It just turns over and over.


Any insight? I pulled the codes again and it's only getting p0320.
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Old 09-09-2010, 04:32 PM   #7
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I would be checking for proper fuel at the fuel rail at this point. If your 2002 still has the Schraeder valve on the fuel rail like my '97 had and my '04 does not, screw a fuel pressure valve on it and see what it says. Factory spec for fuel pressure at the fuel rail (what the fuel injectors plug into) is 49 psi.
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Old 09-09-2010, 04:50 PM   #8
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Thanks Jerry, i had to get a ride from Galveston to Houston so tomorrow I'll get a trailer and pick the jeep up and get it to the house. I will let you know how it goes, thanks again
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Old 09-20-2010, 10:03 PM   #9
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Well guys.... The jeep is running again..... After replacing the crankshaft positioning sensor , throttle positioning sensor, after cleaning every wire harness and connection. After 3 cases of budlight and a few bloody knuckles the problem was found.
After pulling the computers wiring harness out and CLOSELY examining it, I discovered a small area of green corrosion. I'm talking small..... Tip of a pencil small.

Anyway replaced the effing computer for 310$ shipped and programmed from eBay.
She started right up.

Just to be clear here, the crank and throttle sensors didn't fix it but maybe they were due anyway :-)

I really am shocked that the computer got wet actually I guess I'm not shocked, Just annoyed.... Why would jeep put the comp In the engine bay!?!

Jerry thanks for your help and the rest of you.


FYI before seeing the corrosion I was trying to pull codes and every time it would give me some different code. Literally ridiculous codes that made no sense that's why I ended up looking hard at the PCM.

Anyway thanks again guys.

Back to the trails :-)

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camshaft position sensor , crank position sensor , stalling

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