'04 WJ Runs Rough at Startup - JeepForum.com
Sign Up   Today's Posts
User: Pass: Remember?
Advertise Here
Jeep Home Jeep Forum Jeep Classifieds Jeep Registry JeepSpace Jeep Reviews Jeep Gallery Jeep Clubs Jeep Groups Jeep Videos Jeep Events Jeep Articles
Go Back JeepForum.com > Models > Jeep Grand Cherokee & Commander Forums > WJ Grand Cherokee Forum > '04 WJ Runs Rough at Startup

BDS 4-1/2" Suspension Lift Kit - Jeep Wrangler YJRough Country Lift Kits and Parts!FREE, FREE, FREE EVENT!! Save big on Lockers now till Apri

Unread 12-22-2013, 08:43 AM   #1
Registered User
2004 WJ 
Join Date: Sep 2011
Location: Jacksonville, FL
Posts: 351
Wj '04 WJ Runs Rough at Startup

My daughters '04 WJ Sport 4.0 occasionally when started will run super rough. She says it feels like it's going to explode. Most of the time you can turn it off, re-start it and it goes away. I suggested she put a can of Seafoam in the fuel to clean injectors. The spark plugs were replaced a couple years ago. Otherwise the WJ runs well. She just came back from college for XMAS and got 400+ miles to a tankful, so the engine is running efficiently as it has in the past.


2004 Jeep Grand Cherokee Limited 2x4 4.0L
2002 Jeep Grand Cherokee Sport 2x4 4.0L
1998 Jeep Grand Cherokee Laredo 2x4 4.0L
"Three daughters, three Jeeps"
specia1k is offline   Reply With Quote Quick reply to this message
Unread 12-22-2013, 09:38 AM   #2
Web Wheeler
doityourselfMM's Avatar
1999 WJ 
Join Date: Dec 2010
Location: manassas, va
Posts: 1,202
I suspect the problem is electrical. If it was mechanical, the problem would most likely persist. Since turning it off and restarting seems to 'clear' the problem, I don't think it's plugs.

I had a similar idle fluctuation issue. Turning it off and restarting always smoothed the idle out, to a nice flat 550 rpm. I removed the throttle assembly and cleaned. Particularly the IAC valve. So far, so good.

Try the simple (and inexpensive) remedies first. It would probably be wise to install a new throttle gasket after cleaning. Don't over torque (and snap) the 4 bolts.

And don't rule out the Crank Sensor.
doityourselfMM is offline   Reply With Quote Quick reply to this message
Unread 12-22-2013, 09:50 AM   #3
Registered User
2002 WJ 
Join Date: Dec 2004
Location: Irvine, CA
Posts: 883
My 2002 4.0 does this on occasion. I've replaced my battery cables to solve a slow cranking issue and cleaned the intake. When the misfire happens it seems like either an injector or a plug isn't firing. I haven't checked the resistance on the coil or injectors since it hasn't happened in a while. I do run MMO in the tank now for better fuel mileage so maybe it was a sticking injector.

My driving is very consistent and I get 2 MPG better with the MMO. The mileage is apparently dependent on your specific Jeep and the fuel available in your area, some see an increase and others do not. I think the MMO just allows the computer to run more timing on our California fuel.
Upside is offline   Reply With Quote Quick reply to this message

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:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools

Jeep, Wrangler, Cherokee, Grand Cherokee, and other models are copyrighted and trademarked to Jeep/Chrysler Corporation. JeepForum.com is not in any way associated with Jeep or the Chrysler Corp.