Random Misfire #1cyl only - 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 Cherokee & Comanche Forums > XJ Cherokee Technical Forum > Random Misfire #1cyl only

Ruffstuff 10 year saleBDS 4-1/2" Suspension Lift Kit - Jeep Wrangler YJRough Country Lift Kits and Parts!

Unread 03-17-2013, 02:46 PM   #1
Registered User
1999 WJ 
Join Date: Mar 2013
Location: Glover, Vermont
Posts: 2
Random Misfire #1cyl only

1999 Grand Cherokee Laredo 4L random misfire #1cyl only. Coded P0301. Changed spark plugs twice and coils once. Ran fine for a couple of days or weeks after doing this. Then back to the same problem. Starts fine but once the engine has warmed up, the misfire starts when idling in park. The check engine light starts to flash. Can shut it off and it starts up fine again and if you start driving, it drives fine. It will go into the misfire while driving when I am coasting down a long steep hill using the brake. But in the same scenario, if I hit the gas for a quick spurt, it won't go into the misfire. Any thoughts or advice would be great!! Love the old gal and would love to keep her!!

Sheffieldjeep is offline   Reply With Quote Quick reply to this message
Unread 03-17-2013, 06:57 PM   #2
It's the crank sensor!
tjwalker's Avatar
1999 XJ Cherokee 
Join Date: Nov 2007
Location: Central Minnesota, MN
Posts: 8,702
Here are some possibilities. Troubleshooting is a process of elimination; these are suspects.

*Verify fuel pressure. Verify, but for a 99 Cherokee the spec is 49 psi, plus or minus 5 psi. Only takes a few minutes and a fuel pressure gauge can often be rented from many parts stores; call around.

*Swap the fuel injector from cylinder #1 to a different cylinder. If the misfire follows with the swap, you have found the root cause of your misfire.

*Test compression. Not as likely, but can't rule it out. The compression spec. for the 4.0 is 120-150, with no more than a 30 psi variation between cylinders.

*Test your "throttle position sensor".
99 Cherokee, 4.0 AW4, NP242
Past Jeeps: 49 Willys, 81 Scrambler, 88 Comanche
Without "data", all you have is an opinion!
tjwalker is offline   Reply With Quote Quick reply to this message

check engine light , misfire cyl

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.