01 XJ sport with just 54k miles. I keep having random misfires. Only happens after the vehicle has been running a while. I've replaced the plugs and done two seafoam treatments. Took it to the dealer and they confirmed pcm was up to date and everything checked out against the known tsb. They said the compression was a little low and suggested and engine decarb to the tune if 250 bucks thus the previously mentioned seafoam rounds. I'm reading lots of posts about the cps but most of those engines are way over 100k. Any suggestions would be helpful. Thanks!
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01 persistent random misfires
- Thread starter loki36
- Start date
Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
What are the codes you are getting?
larsen
NAXJA Forum User
- Location
- Washington
Sounds like a bad timing chain sprocket (cam drive).
WB9YZU
NAXJA Forum User
- Location
- Madison, WI
Does it only when warm...
Heat soak? I know my 01' is prone to Heat soak on the trail. IIRC Those are generally the codes I get.
Heat soak? I know my 01' is prone to Heat soak on the trail. IIRC Those are generally the codes I get.
- Location
- Minneapolis, MN
Based on what sounds that you have heard in person ?
A faulty CPS will give you random stalling or a no-start. Heat soak is a possibility.
Did you perform the Toothpick Test yet ? http://motorage.search-autoparts.co...estandard//motorage/292005/169830/article.pdf
Did the Dealer look into this, or is that what the $250 is for ?
Chrysler TSB 0900303
1999-2004 with 4.0 L enginer
Multiple Cylinder Misfire due to carbon deposits on exhaust valves.
TSB says an exhaust valve rotation and decarbonization procedure should be performed. http://jsautosource.com/my-projects/tsb-09-003-03-jeep-4-0-engine-running-rough-no-dtc/
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larsen
NAXJA Forum User
- Location
- Washington
None, obviously. Read the post though; misfired on all six with a loud clacking noise. hmm
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Talyn
NAXJA Forum User
- Location
- Radford, Communistwealth of Virginia
Going off the codes it looks like a hot soak or cold misfire (below 50*). When does the misfire happen? After driving a while and letting it sit for some time and they starting it? First start of the day after a cold night? During driving?
Its not a cam gear problem as it isn't a misfire on all six. I see a code for a misfire on #4 and #3, and the random, which pops up with multiple misfire codes. Plus it would be running like crap all the time, not just throwing codes occasionally. Also, there have been a few single row aftermarket cam gear failures, but those have been isolated to strokers with an upgraded valve train. That picture you posted was taken out of context as that is one of the failures on a upgraded valve train with stronger springs and an aggressive cam.
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mongolchuck
NAXJA Forum User
- Location
- Iowa
How are the boots on your coils? Look for white spots on them where the spark could be jumping before reaching the plug. As always, check for vacuum leaks and pinched/burned/chaffed wires. Another good way to spot faulty coils is to spray them lightly with water. If there is a leak the spark will jump and you can usually hear it snap and the engine will buck.
birchlakeXJ
NAXJA Forum User
- Location
- Melrose, MN
The P0300 (random misfire) can also be related to fuel pressure.
Takes all of 5 minutes to check it with a fuel pressure gauge on the fuel rail.
For an 01, you should have 49 psi at idle, plus or minus 5 psi.
Takes all of 5 minutes to check it with a fuel pressure gauge on the fuel rail.
For an 01, you should have 49 psi at idle, plus or minus 5 psi.
