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Old 05-02-2013, 02:46 AM
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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

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Old 05-02-2013, 09:10 AM   #2
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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

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Old 05-02-2013, 12:09 PM   #3
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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 .
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Old 05-02-2013, 01:43 PM
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@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!! =|
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