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Unread 05-24-2009, 08:17 AM   #1
JeepXJ2001
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2001 Xj Misfire 4.0l

OBDII P0304

New coil pack
new head
new gaskets
new h. lifter on missing cylinder
new camshaft positioning censor
swapped the injectors around
tested wiring harness at the injector ends (flashing fine)
checked the computer it looks fine.



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Last edited by JeepXJ2001; 05-24-2009 at 08:29 AM..
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Unread 05-24-2009, 09:18 AM   #2
JeepXJ2001
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A bad O2 sensor or Cat wont cause misfire would they?
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Unread 05-24-2009, 09:21 AM   #3
ddale781
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The 4 in p0304 means that its the 4th cylinder. Said you put in new coil pack? most of the time its something as simple as a bad boot. Try spark plugs? an 02 sensor or cat would not cause this
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Unread 05-24-2009, 10:11 AM   #4
JeepXJ2001
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Quote:
Originally Posted by ddale781 View Post
The 4 in p0304 means that its the 4th cylinder. Said you put in new coil pack? most of the time its something as simple as a bad boot. Try spark plugs? an 02 sensor or cat would not cause this
Yes sir, new spark plugs, new coil pack and I know the code.

What else?
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Unread 05-24-2009, 07:51 PM   #5
JeepXJ2001
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bump me help
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Unread 05-24-2009, 08:07 PM   #6
Jon00XJ
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When you say misfire is it noticable while driving or just on start up?
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Unread 05-24-2009, 08:12 PM   #7
BiggDaddy
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sparkplugs

How did the spark plug in #4 look? I had a misfire in #1 on my 2000 xj. The whole end of the plug was broken/burnt off. Not a clue where it went. I went ahead and replaced all of the plugs. Haven't had the error since, about 6 months now. Good luck.

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Unread 05-24-2009, 09:00 PM   #8
JeepXJ2001
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it looks ok. I changed put new plugs, that was the first thing I did...

Yesterday I checked them again they were ok. I found a thread with people having error p0301.

here is a list of things

Causes

A code P0301 may mean that one or more of the following has happened:

* Faulty spark plug or wire
* Faulty coil (pack)
* Faulty oxygen sensor(s)
* Faulty fuel injector
* Burned exhaust valve
* Faulty catalytic converter(s)
* Running out of fuel
* Poor compression
* Defective computer

Its a long list, i am emptying my pockets on this...
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Unread 05-24-2009, 09:04 PM   #9
mattathayde
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i also found where if you are restarting your motor a few mins after it was hot where the gas in the injector vaporizes and causes vapor lock which leads to the misfire ( i had misfire on 1 and 3 yesterday 2 times but after i cleared it and let the vehicle cool a bit between restarts or restart right away it was fine. the fix if this continues is to insulate the injectors. might not be the same cause for my issue as yours but its one thing to be aware of

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Unread 05-24-2009, 09:23 PM   #10
JeepXJ2001
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it must be a bad valve spring. the rocker arm on the cylinder 4 is loose I think the exhaust one
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Unread 05-25-2009, 12:01 PM   #11
JeepXJ2001
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i went to the machine shop and the owner looked at my valve springs and he concluded that they were fine.

the loose rocker arm is the intake one and the new lifter I put in somehow was springing and it was not tight. Which means that my old one was good and that still i had the same problem
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Unread 05-25-2009, 11:40 PM   #12
filluptrk
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You need compression, fuel, and spark. I'm sure you have checked comp, you can check the injectors for firing with a noid light, and you can take a small thin wire and hook it into the spring connector inside the boot on the rail for the cylinder in question. Put the rail back on and hold that wire close to the head/block etc while someone turns it over. If that one is sparking you should see it as the engine turns over. Phil
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Unread 05-26-2009, 11:39 AM   #13
justanotherjpr
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I get the same error code - in the '00 and '01 it is pretty commonly the fuel injectors heat soaking. Mine is always P0303. Is it all the time, or only when shut down hot and re-started within 10-15 minutes?

Edit: Where did you move the injectors from? IE, no 3 and 4 injectors went to 2 and 5, problem did not follow to 2 and 5.
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Unread 05-26-2009, 12:17 PM   #14
JeepXJ2001
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Quote:
Originally Posted by justanotherjpr View Post
I get the same error code - in the '00 and '01 it is pretty commonly the fuel injectors heat soaking. Mine is always P0303. Is it all the time, or only when shut down hot and re-started within 10-15 minutes?

Edit: Where did you move the injectors from? IE, no 3 and 4 injectors went to 2 and 5, problem did not follow to 2 and 5.
injectors 4 and 2

but the rocker arm is not getting any tension its loose and wobbly in the intake valve.... the guy at the machine shop told me to drop a snake camera in the engine to see if the camshaft is wonred out. but that does not make sense since the problem occurred after the new head installation
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Unread 05-26-2009, 12:22 PM   #15
JeepXJ2001
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Quote:
Originally Posted by filluptrk View Post
You need compression, fuel, and spark. I'm sure you have checked comp, you can check the injectors for firing with a noid light, and you can take a small thin wire and hook it into the spring connector inside the boot on the rail for the cylinder in question. Put the rail back on and hold that wire close to the head/block etc while someone turns it over. If that one is sparking you should see it as the engine turns over. Phil
Last time I checked the compression there was no compression. I put a new lifter and the new lifter needs to be removed and the old one needs to go back since the new one is actually not stiff at all...

I put a brand new coild pack so i should be fine
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