Diagnosing check engine light(2001 w/4.0L) - JeepForum.com
LinkBack Thread Tools
post #1 of 2 Old 07-21-2020, 12:31 PM Thread Starter
Registered User
Bee4570's Avatar
2001 WJ 
Join Date: Mar 2019
Location: Manassas
Posts: 23
Wj Diagnosing check engine light(2001 w/4.0L)

Alright, I should preface this with the fact I'm of....somewhat limited means, but I rather enjoy my Grand Cherokee and I have plans in the future for it(if 2020 can chill the heck out). All the work I've done so far on it has been with the assistance of two different mechanics, as well as my more mechanically-inclined brother. This check engine light thing is getting kinda annoying, however.

Okay, she's a 2001 with the 4.0L, but the original engine was blown and replaced with a good runner out of a 2004 Wrangler. New belts, hoses, timing set, oil pump, water pump, thermostat, ebay header, plugs, coil pack, gaskets. Basically short of pulling the head and rotating assembly, the engine was more or less rebuilt by my own hand.

Now, the check engine light, when scanned, states that cylinder number 5 is misfiring and cylinder 1/bank 1 is running lean(I dunno, that's just what my code reader is saying). Along with that, she's been burning out 02 sensors with....annoying regularity. The newest 02 sensor is maybe 2 months old, the oldest, probably 6 months old. All spark plugs are new, and the first time this combination of warnings was found was what prompted me to replace my coil pack. That fixed it for like, a day.

The engine only has 114,000 miles on it, but the body has more like 176,000 miles on it, and as far as I can tell, it's the factory fuel filter. I've tried to have both different mechanics replace said fuel filter, both have stated extreme reluctance to do so, because the lines going into it appear brittle to their more experienced eyes. I seriously have a brand new fuel filter just rolling around on the floor in the back seat. I also have a set of rebuilt injectors sitting in a tray in my room, basically waiting for the weather to cool off for me to mess with it, because at the suggestion of my brother, it may be a fuel delivery issue.

...what am I missing here? I'm hoping someone here may be seeing what I'm not. Other than the constant check engine light, she starts up, runs and drives just fine. Smooth, mellow little burble(I also had a cat-back exhaust installed when I had the header done because I'm a weirdo like that). She drives great. Not bad for something Tony Stark'd together(Built in a cave, with a box of scraps).

I'll see about getting pictures of the screen of the code reader here in a minute, but any help would be appreciated. This is my daily, and at some point when the world isn't so freaking crazy I'd like to build her into a mild overland trail rig, or at least more than I already have. She's been a great little SUV, but I'd rather not let something like this sit until it becomes a major problem.

Private Sign - Do Not Read
Bee4570 is offline  
Sponsored Links
post #2 of 2 Old 07-21-2020, 12:43 PM Thread Starter
Registered User
Bee4570's Avatar
2001 WJ 
Join Date: Mar 2019
Location: Manassas
Posts: 23
Well, she's throwing up only the one trouble code now, so I guess that's a good thing?
Attached Thumbnails

Private Sign - Do Not Read
Bee4570 is offline  

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome