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Discussion Starter · #1 · (Edited)
Im about done.... I have been having the p300 thru 306 misfire codes.
Heres what ive done.

New items...
bat
gas cap
spark plugs ngk mopar recommend
Coil pack
cam sensor
crank sensor
magnaflow hi flow cats
headers
muffler
air filter
Clydr head
Vacuum tubing
injector heat shields
injector o rings

Things ive checked
fuel pressure
compression
leak down test
cam n crank positioning
seafoam through intake. Intake totally cleaned during head replacement bottle's of lucus fuel stab n cleaner
throttle body cleaned like new




Im sure theres alot more ive replaced and done over the last 2 weeks things left I could do? Just replace injectors? Ecm? O2 even though it's not throwing an o2 code? Dunno im out 4 grand as of today.
 

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Im about done.... I have been having the p300 thru 306 misfire codes.
Heres what ive done.

New items...
bat
gas cap
spark plugs ngk mopar recommend
Coil pack
cam sensor
crank sensor
magnaflow hi flow cats
headers
muffler
air filter
Clydr head
Vacuum tubing
injector heat shields
injector o rings

Things ive checked
fuel pressure
compression
leak down test
cam n crank positioning
seafoam through intake. Intake totally cleaned during head replacement bottle's of lucus fuel stab n cleaner
throttle body cleaned like new




Im sure theres alot more ive replaced and done over the last 2 weeks things left I could do? Just replace injectors? Ecm? O2 even though it's not throwing an o2 code? Dunno im out 4 grand as of today.
I'm more or less in the same boat . I'm thinking ( at lest on mine) it's an injector or computer issue
 

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I would think about the same thing its got to be either computer issue or injector. I would lean more towards a computer issue since you get all te missfire codes.
 

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I got hell misfired on my 2006 range rover.....spent lots of $$$$ at the dealer. Changed almost everything still get misfired codes. In the end second dealer found blown gasket was the caused of misfired hell. I hope it s not the same issue on your jeep.
 

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Im about done.... I have been having the p300 thru 306 misfire codes.


Im sure theres alot more ive replaced and done over the last 2 weeks things left I could do? Just replace injectors? Ecm? O2 even though it's not throwing an o2 code? Dunno im out 4 grand as of today.
:wavey:Rubikhan: Is it still throwing / started throwing those same codes after replacing all of the above?
 

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Exactly what brand & model # spark plugs did you install? And to be sure, a bad 02 sensor will not necessarily cause a CEL... the computer can't always tell if it is being misled by a bad 02 sensor.
 

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K...A thought for you and it might sound strange (probably will get :bottom:for this) but I had a problem with bearings being worn out in my belt pulley...it was not allowing it to generate enough electrical current for the ECM to process correctly.

Looks like you did some searches (only thing I don't see replaced is the four 02's & ECM but I might have overlooked something in your list) Did a few searches on "P codes" in the forums and there were more than a few that the problem ended up being "electrical" including a recall for programming the ecm because of misfire.
 

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Exactly what brand & model # spark plugs did you install? And to be sure, a bad 02 sensor will not necessarily cause a CEL... the computer can't always tell if it is being misled by a bad 02 sensor.
lol...I was just going to ask where is Jerry:D
 

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Replace injector, Pull fuel line from the fuel tank and flush fuel line. I had the P301 and replaced the injector, and the code threw again. Did a fuel system flush.. More crap came out of that then I've seen ever before.. So try a fuel system flush..
 

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have you replaced your distributor cap and rotor button? I had a misfire and did plugs, wires, o2 sensors and then dist cap and rotor button last and those were the parts that fixed it.
 

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have you replaced your distributor cap and rotor button? I had a misfire and did plugs, wires, o2 sensors and then dist cap and rotor button last and those were the parts that fixed it.
He dos not have those parts. His Jeep has DIS (Distributerless Ignition System.)
 

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The coolant temperature sensor could be out of wack. The easy way is to use a scan tool that can read the engines current imput data. Ive had some fail to where the computer thought it was -100 degrees when it was 60 degrees outside. Which caused the computer to give way more fuel than it needed causing a multiple cylinder misfire.

You may have already but you might use a timing light to see if the misfire is spark related.
 

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Discussion Starter · #14 ·
Ill look into all these ty. Jerry im using the mopar ngk plug. I cant remember number when I ger off work ill try to find the number something like n9 or n6 something something
 
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