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Unread 12-28-2012, 10:11 PM   #1
Kali01
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HELP! misfire gremlin

I've been chasing a gremlin in my 2001 Jeep Cherokee for almost 6 months now. symptoms are as follows:
-on a cold start it'll run like hammered ***. CEL flashes, multiple cylinder misfire (always cyl. 3 and others are randomly dropped) up to 3 at one time.
-if you let it get to running temp (it can't just idle I've tried; you have to actually drive it) turn it off for 2 minutes and turn it back on she runs like a completely different vehicle. CEL is still on but not flashing, idles a little rough but not bad enough for anyone but myself to notice.
-as long as the engine doesn't cool completely she'll run fine for the rest of the day.
list of things i've already tried to avail:
-new plugs, all NGK
-new injectors (they were old anyway. i figured why not?)
-new coil pack
-new ECM
-new crankshaft position sensor
- i have a heat shield on cyl. 3/manifold/fuel rail.
compression tests check out fine. noid test on injector wires are fine. I really don't want to sell but i might have to if i can't figure this out.

just put in a remaned long block in june. does anyone have any ideas?

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Unread 12-28-2012, 10:15 PM   #2
Mean Max
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Check out the TSB in my thread. It has solved issues on 2 Jeeps in my shop.

http://www.jeepforum.com/forum/f310/...issue-1450392/

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Unread 12-28-2012, 10:21 PM   #3
CJ7-Tim
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Quote:
Originally Posted by Kali01 View Post
....... just put in a remaned long block ..........

Check the cam sensor synchronization.

Read this -> http://jeep.blackonyx.net/pdfs/jcss.pdf
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Unread 12-28-2012, 10:22 PM   #4
Kali01
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my problem is pretty much the complete opposite. once the engine is warm it runs fine, only when it's cold does it throw fits.
and unfortunately i already have a heat shield
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Unread 12-28-2012, 10:22 PM   #5
Tkoffroad
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Have the same problem except mine is cylinders 6
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Unread 12-28-2012, 10:32 PM   #6
Kali01
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Quote:
Originally Posted by CJ7-Tim View Post
Check the cam sensor synchronization.

Read this -> http://jeep.blackonyx.net/pdfs/jcss.pdf
that was extremely helpful. i'll have to suggest that to my mechanic. thank you
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Unread 12-29-2012, 12:09 PM   #7
Kali01
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still no luck. someone suggested that a relay from the computer to the injectors could be bad.
i didn't even think about it being an electrical issue. sound plausible?
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Unread 12-29-2012, 12:17 PM   #8
buildin1XJ
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What are the exact codes you have now?
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Unread 12-29-2012, 01:35 PM   #9
GetLifted
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Quote:
Originally Posted by Kali01 View Post
still no luck. someone suggested that a relay from the computer to the injectors could be bad.
i didn't even think about it being an electrical issue. sound plausible?
Mine was very similar. It was electrical. I discovered the problem on page 3 and 1000$ later...
http://www.jeepforum.com/forum/f11/w...45/?highlight=
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Unread 12-29-2012, 07:38 PM   #10
Kali01
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Quote:
Originally Posted by GetLifted View Post
Mine was very similar. It was electrical. I discovered the problem on page 3 and 1000$ later...
http://www.jeepforum.com/forum/f11/w...45/?highlight=
so basically i need to check the grounds around the crankshaft position sensor and while i'm at it check the other grounds as well. i read the whole thread, found myself laughing when you said you were praying for a blown head gasket too... if only it were that simple. :/
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Unread 12-29-2012, 08:00 PM   #11
GetLifted
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Not really a "ground" to check, but the resistance in the wires from the PCM connector to the cam and crank sensors. The sensors don't chassis ground, they are a return signal to the PCM.
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Unread 12-29-2012, 08:08 PM   #12
Kali01
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also, i would like to reiterate that the problem isn't with hot starts; once it's at 210 she'll run all day. only at a cold start like after sitting over night will the gremlin rear it's ugly head and then once it reaches running temp you can turn it off let it sit for a couple minutes turn it back on and she runs fine.
only PO300 codes are being thrown.
i have tried everything i know how to do and have had it seen by two shops. she's with a jeep specialist (worked for chrysler for 20 something years/jeep enthusiast) and he's coming up empty handed too.
it's got to be something small, something i'm overlooking, electrical most likely. but where?!?!?!?!
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Unread 12-29-2012, 09:19 PM   #13
GetLifted
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To test the harness:
Unplug the PCM c1 connector. Unplug the cam AND crank connector plugs at the sensors. Use a multimeter set to 0-10k ohms resistance. Probe the PCM C1 PIN4 HOLE (black/blue stripe) with one end of the meter, with the other end of thr meter probe the black/blue stripe wire at the cam and crank sensor and MAKE SURE it's zero ohms (they share a sensor return/ground).

You can use this procedure for any part of the harness. T-pins fit in the PCM connector holes perfectly. Alligator clips snap on to the pin. It's explained in the thread I posted with pictures.
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Unread 12-30-2012, 12:27 AM   #14
mmcc
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I had a missfire in mine a little ways back. My buddies and I evenualy pulled a cam position sensor of his jeep and we replaced the platinum spark plugs with cheaper copper ones. The jeep ran great after that. I know plugs sound crazy, but its a cheep enought thing to just through a couple of bucks
at and pray it works. My .02.
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Unread 12-30-2012, 08:59 AM   #15
Kali01
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Quote:
Originally Posted by GetLifted View Post
To test the harness:
Unplug the PCM c1 connector. Unplug the cam AND crank connector plugs at the sensors. Use a multimeter set to 0-10k ohms resistance. Probe the PCM C1 PIN4 HOLE (black/blue stripe) with one end of the meter, with the other end of thr meter probe the black/blue stripe wire at the cam and crank sensor and MAKE SURE it's zero ohms (they share a sensor return/ground).

You can use this lrofedure for any part of the harness. T-pins fit in the PCM connector holes perfectly. Alligator clips snap on to the pin. It's explained in the thread I posted with pictures.
thank you so much! only problem is the shop won't open again till wednesday due to new years :/ ugh... patience is a virtue i was not blessed with


thanks to everyone who tried to help. i'll post updates when i know something.
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flashing cel , misfire , rough start

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