2001 XJ P0305 misfire - Help
07-01-2010, 11:01 PM
#17
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Hey that was the first on your list. My bad. I wouldn't give up. If the body and everything is in good shape, why not do a motor swap? You could get an 4.0 for like $1500, or you could buy a stoker. 
07-01-2010, 11:13 PM
#18
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Year: 2000
Model: Cherokee
Engine: i-6 4.0
I dont think it would be this, but you have checked a whole lot of things it could be. The wires for the injectors, follow them back and make sure the wiring is all good and theres no shorts or breaks in them. And make sure you didnt accidently swap the connectors for the injectors. Im not sure how much this matters, but i do know each one has a different color wire from the rest.
07-01-2010, 11:29 PM
#19
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Engine: 4.0L
if you got the connector crossed it would definatly be misfiring. but i dont think they will reach the wrong injector. I thought i read something in here about the heads cracking in between cylinders just a thought. could you have a leaky intake gasket at that cylinder? i usually check for those with a can of brake clean spraying it around and the intake right there on the runner and monitor the o2 sensors to see if they change if the brakeclean is getting pulled into the cylinder it will cause a drastic change in your o2s. ( your mech should know how to do that). jmho
07-02-2010, 12:36 AM
#20
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Year: 2000
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Engine: i-6 4.0
if you got the connector crossed it would definatly be misfiring. but i dont think they will reach the wrong injector. I thought i read something in here about the heads cracking in between cylinders just a thought. could you have a leaky intake gasket at that cylinder? i usually check for those with a can of brake clean spraying it around and the intake right there on the runner and monitor the o2 sensors to see if they change if the brakeclean is getting pulled into the cylinder it will cause a drastic change in your o2s. ( your mech should know how to do that). jmho
07-02-2010, 06:58 AM
#21
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Year: 2001
Model: Cherokee
Engine: 4.0
to OP, you had said that the missfire got worst? was it after the plug change? if so regap the plugs its free to do and look in there a see if you missed anything...
the only thing i can tell you is that in my 2001.. my ecu has been reflash at the dealer theres a sticker on my fender with numbers and dates..
good luck man
the only thing i can tell you is that in my 2001.. my ecu has been reflash at the dealer theres a sticker on my fender with numbers and dates..
good luck man
07-02-2010, 07:14 AM
#22
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I finally took it to the dealer and they diagnosed the PCM was causing the misfires. The dealer wanted close to 1000 for a new computer so I looked on ebay and got a refurbished one flashed with updated firmware and programmed with my VIN number for 150. Poped it in and guess what, it STILL is misfiring! The dealer did put in a heat shield for free to cover the recall, but that obviously did help the misfire. Any other ideas is appreciated before I sell it for what I can get for a misfiring 2001 jeep cherokee sport. Maybe $3k.. any takers? So far I did the following:
New Plugs
New coil pack
New PCM (computer)
Heat shield
Injector noid test
Swapped injectors
Compression check (135)
Seafoam
Fuel pressure test
Oil pressure test
Hydrocarbon test
and took to a Jeep dealer for diagnosis
New Plugs
New coil pack
New PCM (computer)
Heat shield
Injector noid test
Swapped injectors
Compression check (135)
Seafoam
Fuel pressure test
Oil pressure test
Hydrocarbon test
and took to a Jeep dealer for diagnosis
I had a similar problem with my 2001 and it turned out that the head was cracked. I did not know that the 2001 has an aluminum head that is susceptible to cracking.
07-02-2010, 10:30 AM
#23
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to OP, you had said that the missfire got worst? was it after the plug change? if so regap the plugs its free to do and look in there a see if you missed anything...
the only thing i can tell you is that in my 2001.. my ecu has been reflash at the dealer theres a sticker on my fender with numbers and dates..
good luck man
the only thing i can tell you is that in my 2001.. my ecu has been reflash at the dealer theres a sticker on my fender with numbers and dates..
good luck man
07-02-2010, 10:36 AM
#24
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Year: 1994
Model: Cherokee
Engine: 4.0
i have also read something about "heat soak" on the newer ones. something todo with the intake manifold getting to warm. but it usually effects the 2 inner most cylinders. Try some form of heat insulation between the exhaust and intake mani. Even if it doesnt fix you problem it will help with power and mpgs
07-02-2010, 10:39 AM
#25
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07-02-2010, 10:41 AM
#26
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Year: 1990
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Engine: 4.0 lt. 242 cu.in.
Noid testing the injectors only confirms that the solenoid in the injector is working. It does not accurately tell you is the injectors are spraying or not. My guess is a clogged injector.
Edit: If it happens when the engine is cold then it isn't heat soak.
Edit: If it happens when the engine is cold then it isn't heat soak.
Last edited by offroadnut36; 07-02-2010 at 10:43 AM.
07-02-2010, 10:51 AM
#27
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07-02-2010, 11:13 AM
#28
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Year: 1996 Sport
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Engine: 4.0L H.O.
check the cat, o2 sensors and your exhaust back pressure....could be bad/plugged up cat building up pressure in exhaust manifold and cylinders...but it would generally start with the last cylinder....worth a try....good luck!
07-02-2010, 11:35 AM
#30
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Year: 1996 Sport
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Engine: 4.0L H.O.