Started misfiring and oil pressure shot all the way up...
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
I've been having misfire issues. Especially at idle. I changed the plugs, coil, and cleaned the IAC and throttle body. It always starts missing at random times and today it decided to on my way home. Only this time I noticed that the oil pressure shot all the way up so I pulled over, turned it off, and checked the oil. The oil smells like pure gasoline so I had it towed home. Any idea on what could cause this? Injectors?
Junior Member
Joined: Mar 2009
Posts: 95
Likes: 0
From: Western Colorado
Year: 1988
Model: Cherokee
Engine: 4.0l
The first thing I'd check is the fuel pressure regulator, it could be building up to much pressure, pull the vacuum line and start it to see if fuel comes out
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
CF Veteran




Joined: Nov 2010
Posts: 5,839
Likes: 116
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
Put a fuel pressure gauge on the schrader valve on the fuel rail. With an 00, you should have 49 psi, plus or minus 5 at idle. Many big box parts stores will rent you the gauge.
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
Thanks for the information. I already ordered injectors. They should be here today but I don't want to put them on and waste 300 dollars. I am a college student so that's a nice chunk for me. I'm headed to advance auto parts now.
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
I'm supposed to be on my way home for fall break and I can't leave until this thing is fixed. It's worse than ever now. Idles fine, shutters when put in gear, and the oil pressure shoots up slowly as soon as you give it gas. I've tried everything here with no results. Any other ideas?
Trending Topics
Member
Joined: Sep 2011
Posts: 141
Likes: 0
From: North Chicago
Year: 1993
Model: Cherokee
Engine: 4.0
Take the vacuum line off that goes to the regulator and start it. You will probably find that it leaks gas out of the vacuum fitting, meaning that it is dumping gas into the engine.
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
Originally Posted by andyg
Take the vacuum line off that goes to the regulator and start it. You will probably find that it leaks gas out of the vacuum fitting, meaning that it is dumping gas into the engine.
Senior Member
Joined: May 2009
Posts: 800
Likes: 3
From: The Dirty 530
Year: 1988
Model: Cherokee
Engine: 4.0 Renix I6
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
I found the problem. One of the wires coming from the computer to the coil was shorting out. Fixed that and it runs like a champ.
BUT now I have another problem. Ever since I fixed that, it will only idle for about 30 seconds before it dies. There's no check engine light or anything. It has made quite a few people mad at red lights and is irritating me. The coil is brand new, the plugs are brand new (Autolite Platinums) and my misfire is gone. I'm stumped.
BUT now I have another problem. Ever since I fixed that, it will only idle for about 30 seconds before it dies. There's no check engine light or anything. It has made quite a few people mad at red lights and is irritating me. The coil is brand new, the plugs are brand new (Autolite Platinums) and my misfire is gone. I'm stumped.
Thread Starter
Newbie
Joined: Oct 2011
Posts: 13
Likes: 0
From: Gulf Coast, MS
Year: 2000
Model: Cherokee
Engine: 4.0
CF Veteran




Joined: Nov 2010
Posts: 5,839
Likes: 116
From: In the middle of Minnesota!
Year: 1999
Model: Cherokee
Engine: 4.0
There are a number of possibilities for stalling, but one of the primary ones is a "marginal" battery. And yes, you CAN have a battery that is strong enough to start the engine, but marginal enough to give the engine management system fits and create "stalling" Have the battery LOAD TESTED. Any parts store will do this for you for free.
It could be something else, but failure to verify the battery early in the troubleshooting process is a mistake.
It could be something else, but failure to verify the battery early in the troubleshooting process is a mistake.


