4.0L Multiple Misfire P0300 HELP! - Jeep Wrangler Forum
Jeep Wrangler Forum

Go Back   Jeep Wrangler Forum > TJ Jeep Wrangler Forum > TJ Tech Forum

Join Wrangler Forum Today

Thread Tools

Please support our sponsors and let them know you heard about them on WranglerForum.com
Old 05-02-2013, 02:46 AM
Thread Starter
Join Date: May 2013
Posts: 4
Exclamation 4.0L Multiple Misfire P0300 HELP!

I have a 2000 Jeep Wrangler 4.0L, It is misfiring MIL light on, codes are P0300, PO304, PO303 for Multiple Misfire. Here are the following repairs I have done:

*Replaced Ignition Plugs
*Replaced Ignition Coil Pack
*Replaced a Blown Headgasket
*Had Cylinder Head Machined (New Hardware, Headbolts n Valve Guides)
*Used Combustion Cleaner to Clean all deposits in Combustion Chamber
*Checked Fuel Pressure = OK
*Checked Compression = ALL Cylinders OK
*Checked PCM Harness Injector pulse with Noid Lights = Ok
*Checked for Vacuum Leaks = Ok
*Swapped Injectors for Known Good Injectors = OK

It can last up to a day and a half with the MIL light off, but eventually will turn on. Need to SMOG car soon. ANY SUGGESTIONS, APPRECIATE IT! Thanks

TJ831 is offline   Quote
Old 05-02-2013, 09:10 AM   #2
Supporting Member

5-Year WF Supporting Member
Evpjr's Avatar
Join Date: May 2012
Location: Bakersfield
Posts: 1,754
It sounds like you are pretty thorough and are not a newcomer to a Jeep, so only thing I can suggest is to check all of the wiring to the sensors, making sure none of the wires are cracked, pinched, or laying on a hot exhaust pipe and arcing through

Evpjr is offline   Quote
Old 05-02-2013, 12:09 PM   #3
Join Date: Aug 2011
Posts: 140
replaced the plugs in my tj 4.0 cause of misfire on startup and bad mpg. did the adaptive memory reset and now it runs silky smooth on startup but haven't had it done long enough to check mpg yet .
chemicaljeep is offline   Quote
Sponsored Links
Old 05-02-2013, 01:43 PM
Thread Starter
Join Date: May 2013
Posts: 4
@Evpjr Thanks , After reading a million Jeep Forums I came to the conclusion that it may be my Crank Position Sensor, though i will still check all wiring. @chemicaljeep What kind of plugs did you install? What codes did you get if any? Going back to work on it today. Wish me Luck!! =|
TJ831 is offline   Quote

Thread Tools

Posting Rules
You may not post new threads
You may not 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 Off
Refbacks are Off

All times are GMT -5. The time now is 03:01 PM.

Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2019, vBulletin Solutions, Inc.
Search Engine Optimization by vBSEO 3.6.1
User Alert System provided by Advanced User Tagging v3.1.0 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.

Jeep®, Wrangler, Liberty, Wagoneer, Cherokee, Gladiator, Mopar and Grand Cherokee are copyrighted and trademarked to FCA US LLC.
Wranglerforum.com is not in any way associated with FCA US LLC.