misfire code that won't die..tried the obvious fixes - Jeep Commander Forums: Jeep Commander Forum
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post #1 of 10 (permalink) Old 08-30-2011, 12:41 PM Thread Starter
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Unhappy misfire code that won't die..tried the obvious fixes

Long time listener, first time caller here. I have a 2007 Jeep Commander, 5.7l V8 Hemi. 88,000 miles. Started getting a misfire on cylinder 4 code last week. Changed the plugs (with Champion 570 copper plugs), changed out the coil pack, replaced the fuel injector for that cylinder, changed the oil (5/20 synthetic) and then replaced the MDS solenoid. When the MDS solenoids were accessible- it appeared a rodent chewed some wires and shorted out the solenoid- fixed the wires. I am obviously out of warranty so this is a DIY work in progress. Engine is still missing, Check engine light still comes on, still getting a misfire code on cylinder 4. Could the ECM have been shorted out too and therefore continuing to shut down the 4th cylinder?? BTW- when the intake was off for the MDS Solenoid swap out, noticed that the cylinder was alot cleaner then the others ??? Any thoughts?

Any suggestions??
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post #2 of 10 (permalink) Old 08-30-2011, 04:54 PM
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The code is for the 4th cylinder in the firing order.....not cyl#4

Firing order is 18436572......possible you are messing with the wrong cylinder?

Rob


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post #3 of 10 (permalink) Old 08-31-2011, 05:56 AM Thread Starter
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Unfortunately no. All of the work was done on cylinder 3. (4th in firing order)
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post #4 of 10 (permalink) Old 08-31-2011, 07:16 AM
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Good!
One of those things I had to ask.

What was the compression on that cyl? The clean intake port gets my attention as well....a bit cleaner OK just a variation, a lot cleaner usually means a valve seal that isn't but that generally won't make a misfire.

Since you had the manifold off and resealed that takes the intake port vacuum leak out of the equasion unless the manifold has a hairline crack that was overlooked.

Back to compression test.

Rob


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post #5 of 10 (permalink) Old 09-06-2011, 11:57 AM Thread Starter
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Didn't do a compression test. I'll have to get the tool to do that and get back to you. What about my ECM idea?? Do you think getting the dealer to reprogram it will help? (since the MDS solenoid was shorted out by the exposed wires)
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post #6 of 10 (permalink) Old 09-06-2011, 03:09 PM
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Just a thought, never heard of this before until it happened. On our Dodge Dakota it was misfiring, did all the replacments we could think of. Deceided that since it wasn't running right anyway to pull the valve cover, found out that the rocker arm fell off. Guess they just push on. Was told that if the engine rotates backwards (as in doesn't start like with a remote starter) they will pop off. Put back together runs fine except the check engine light won't go off. Still says there is a misfire.

Jeff
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post #7 of 10 (permalink) Old 09-06-2011, 03:31 PM
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Reprogramming a PCM (ECM) will NOT fix it, if its suffered damaged from a short, only replacing it will fix the damage.

In my '99 Neon R/T, I had a short in the wiring for one of the injectors, kept blowing the fuse for the PCM/Fuel Pump. It left me stranded 200 miles from home, I had mis-fire codes and a fuel injector circuit code. I decided to risk it and put in a bigger fuse (yes, the thing they say never to do) and it kep the motor running without blowing. When I fixed the short, I still had the same problem, this time with codes for "Fuel Injector Driver" that is a part of the PCM.

Sure enough, using the bigger fuse let the short fry the part of the PCM that does the amplifying/driving of the fuel injector circuit. Since I had put an aftermarket PCM in my Neon R/T, I still had the OEM PCM on the shelf, put it in and it ran just fine. It was one part of the PCM that was fried.

BUT, I had codes for "Fuel Injector Driver", NOT just symptoms of something on the engine NOT working right. There are a lot of people that waste money on new PCM's/ECM's because they jump to conclusions and assume the PCM went bad. Good luck, I don't know of any test for the drivers on the PCM that wouldn't involve something like a ocilliscope, hopefully there is some test out there to confirm it.

And sadly, with the Anti-Theft Measures, I don't think you can replace the PCM yourself, the dealer starscan tool is required to program it for you vehicle and enable it. I don't think it will start or drive, until you get it to the dealer, meaning you likely have to pay them to replace it as well, they won't let you do it in their parking lot and bring the tool out into the parking lot. (That is one that has some justification, I will continue to rant about the others that have no justification to pull this kind of crap).


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post #8 of 10 (permalink) Old 09-27-2011, 08:02 PM
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i think your messing with the wrong cylinder. i assume the code is P0304 correct? that means, CYLINDER NUMBER FOUR!!! NOT NUMBER THREE!!! that code is telling you what cylinder. NOT what cylinder in a firing order. that just plain does NOT make sense. try looking at cylinder FOUR!!!
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post #9 of 10 (permalink) Old 04-04-2012, 01:39 PM Thread Starter
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Talking

Thought I'd let you guys know that it's finally fixed! It was a bad lifter. The lifter was all jammed up. The push rod bent and lodged in by the rocker..so after pulling the head and replacing the lifter (which was on back order for almost 2 months), the valve, the rocker arm, the push rod,etc...she is running great. No ticks, no codes, no engine light.
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post #10 of 10 (permalink) Old 04-04-2012, 09:58 PM
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Good to hear!!!

2006 jeep commander many mods.
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