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Unread 06-27-2011, 12:51 PM   #1
fedx95
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now im confused...misfire

hey, lets see if we can figure this one out: (4.0 HO 1996 XJ Cherokee)
i took my jeep wheeling for a few hours. As i left the premises, it idled like crap and died on me. Let it sit b/c the paper filter was soggy. Later realized the main ground to the body was broken too. Ever since, it has been misfiring (i think). I am not getting any codes at all (except for my speed sensor code)
Heres what i've done:
replaced air filter with a cone style one
replaced the ground coming immediately out of the battery (with 4 gauge)
ran fuel injector cleaner
tightened all my spark plugs (they were loose!)

the misfire seems to be in and out. Some days it runs ok. Other days, it wants to die all the time.

When i start it, it will idle at 1250 rpms, slowly drop down to around 800. Then it starts misfiring. it will sputter, drop to 250rpms, then shoot back up to 1500. Sometimes, the sputter is great enough to stall it.
It does sputter while giving it gas too.
Can this be the TPS or CPS, or anything else?

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Unread 06-27-2011, 12:56 PM   #2
AmbuGrl
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You tightened the spark plugs? I would go ahead and replace them now. CHeck the wires to your upstream O2 sensor as well. I beleive that there is a write up on here on how to check your CPS. But that would generally cause it to not start at all.
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Originally Posted by RacerX View Post
WTF is Clockspring??? my Jeep has digital clock
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Unread 06-27-2011, 08:36 PM   #3
fedx95
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the wires to my upstream o2 were shorting. I taped them up. Took it wheeling, and it was misfiring so bad, it was practically undrivable. I had to keep my pedal on the gas so it wouldn't die. It also didn't know when to shift. Without touching the pedal cruising at 40, it was shifting like crazy between 2 and 3 gear. My rpms were going from 2k to 4.5k and back. Everyone was staring like it was about to blow up. On the way back, however, it fixed itself for about 5-10 minutes. No misfires and shifting fine. Then it went haywire again.

To cold start it usually doesn't do it on the first try. It always did before. Even when its warm it might do it on the second try. My throttle body is dirty, i checked it today. Its got a layer of soot. No big particles however
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Unread 06-27-2011, 08:47 PM   #4
AmbuGrl
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Taping them wont fix the problem with them and they are more than likely the cause. You need to splice new ones in and cut the bad parts out.
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I drive an XJ, and all of my power windows work :)



2000 Pontiac WS6 - DD
DD (Mine) Sold - 98 XJ Moss Green
(His) - 92 YJ December 2013 YJOTM

Sold - 95 ZJ
Sold - 97 XJ Red
Sold - 98 XJ


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NAXJA #3700

Quote:
Originally Posted by RacerX View Post
WTF is Clockspring??? my Jeep has digital clock
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Unread 06-28-2011, 12:00 PM   #5
fedx95
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The bad part was only a 2" section b/c it rested on the exhaust manifold. It wants to idle low, around 450 rpms when its not misfiring. If you give it a touch of gas and then let off, it will die. Also, it always started on one turn of the key (about 3rd or 4th crank). Now i have to turn the key three or four times before it will start(about 9 cranks per turn).
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Unread 06-28-2011, 04:49 PM   #6
fedx95
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i disconnected the o2 sensors. I got these codes
12, 21, 21, 42, 25
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Unread 06-28-2011, 07:03 PM   #7
SXIPro
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Change your plugs. 12 bucks worth of Champions and you may be all set. Worked on mine which was misfiring on cylinder 6. Tossed all the crappy Bosch plugs in the trash. Those things are worthless.
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Unread 06-28-2011, 10:35 PM   #8
fedx95
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ill be changing the plugs then tomorrow. Anybody have any idea on whats causing the codes?
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Unread 06-29-2011, 04:07 PM   #9
fedx95
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The Good:
the positive from the battery to the fusebox was loose. I tightened it and it idled at the correct speed. Still died when the misfire kicked in.
The Bad:
changed the plugs to champions. replaced the distributor cap as well as rotor, which had some condensation a few days ago when i checked it.
Got home today, left it running as i walked out of the car. There was an awful racket coming out of the throttle body. Pulled the filter out and that made it louder. Then it turned off n.
I went to turn it back on, but it wont. You can hear one or two combustions but it doesn't catch.

It won't shift most of the time until the rpms are at 4500. My fuel economy has tanked. I burned half a tank for about 30-50 miles of driving. Since i disconnected the battery to refresh the loose positive, the codes are gone. I reconnected the upstream 02 sensor. Now i got the codes 12, 15, 21, and 24

the car is currently not running and its frustrating

the downstream o2 is not attached to the exhaust, b/c i am running a "modified" exhaust. It has been that way for 5 months without any issue.
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Unread 06-29-2011, 09:31 PM   #10
fedx95
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i primed it by turning the key to on a few times waiting a few seconds, and turning it back off. It started again. I noticed that when i primed it, i could hear the fuel pump whining like it should. Thing is, i cycled the ignition 5 times, but i didn't hear the pump for 2 of those times. That leads me to conclude that my fuel pump is bad and thats whats causing the misfire. Any thoughts?
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Unread 06-30-2011, 06:58 AM   #11
fedx95
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....
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Unread 06-30-2011, 09:04 PM   #12
fedx95
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update. Made the same wierd noise in the throttle body. Then i turned it off. Didn't start after that. It is running hot. I don't know if that has to do with the cooling system. I don't hear the fuel pump whine at all now.
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4.0 , cherokee , misfire , rough idle , xj

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