Random Misfire and Cyl#4

AndrewG27

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My car has been acting rather strange lately, I found that if I cruise at about 3200 rpms for about 5 seconds then the check engine light will start to flash and the car will start to sound like it is running on very little power.

I had this happen on the freeway, the light flashed for about 20 seconds and then went away and the car drove fine again. I then put the car in 5th again and hovered at 3200 and it did the exact same thing. This time it left the check engine light on and the codes were for random misfire and misfire on cyl#4.

Don't have much to go on as to why this is happening. The only thing that happened specifically to that cylinder is that an extension arced from the battery to the #4 spark plug coil hole in the head. But i didn't think that would cause this. Unless the arc could have affected the spark plug.

It's really weird that it only happens at about 3200 rpm. If I run it at 2800 or 4000 it doesn't ever throw a code.

Hopefully you guys can help figure this out.
Thanks
 

chuck@evoperform

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I assume that you were checking or changing plugs and didnt disconnect the battery? Very bad. You may have screwed the PCM up. I have seen it happen before.
 

AndrewG27

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Yeah basically what happened. I had the negative disconnected but i wasn't paying attention and it moved back to the neg post and then it arced. Just really strange it only happens at that specific spot. Never skips a beat anywhere else.
 

JAJ

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...The only thing that happened specifically to that cylinder is that an extension arced from the battery to the #4 spark plug coil hole in the head...

I'm having trouble visualizing what happened. Did you have the coil out of the hole and you were undoing the spark plug when the ratchet handle hit the battery + terminal? Or what?

Have you considered the possibility that you were so distracted by the sparking and other chaos that you didn't tighten the plug properly or that the connector might be loose or something that can cause a miss that wasn't caused by the arcing? Or, if you were changing the plugs, maybe it's a defective plug.
 

Wnt2gofst

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My 2011 had this issue. Never arced anything. Did it bone stock. Dealer just threw all kinds of parts at it till it fixed it. Plugs, coil, new pcm, injectors.

Samsung Galaxy 2-better then your iPhone..
 
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tmcolegr

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My car has been acting rather strange lately, I found that if I cruise at about 3200 rpms for about 5 seconds then the check engine light will start to flash and the car will start to sound like it is running on very little power.

I had this happen on the freeway, the light flashed for about 20 seconds and then went away and the car drove fine again. I then put the car in 5th again and hovered at 3200 and it did the exact same thing. This time it left the check engine light on and the codes were for random misfire and misfire on cyl#4.

Don't have much to go on as to why this is happening. The only thing that happened specifically to that cylinder is that an extension arced from the battery to the #4 spark plug coil hole in the head. But i didn't think that would cause this. Unless the arc could have affected the spark plug.

It's really weird that it only happens at about 3200 rpm. If I run it at 2800 or 4000 it doesn't ever throw a code.

Hopefully you guys can help figure this out.
Thanks

specifically what DTCs were set in the PCM?

might want to review:

http://s197forum.com/forum/showpost.php?p=900442&postcount=95

http://s197forum.com/forum/showpost.php?p=1022564&postcount=106
 
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chuck@evoperform

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Yeah basically what happened. I had the negative disconnected but i wasn't paying attention and it moved back to the neg post and then it arced. Just really strange it only happens at that specific spot. Never skips a beat anywhere else.

I hate to say it but there is a good chance that the ECU will need to be replaced. Saw where the same thing happened on an 11 GT500 and after chasing issues for 2 weeks, the ECU was replaced and apparently the problem went away.

Electronics can be very funny in how they act when they have been damaged. When you short the positive terminal to the plug, the current will follow the path of least resistance, but there is still going to be a good amount of current that will find its way through the ECU via various sensors.
 

wproctor411

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That sucks. I wonder I a used PCM could be sourced from a 2011/2012 junker.
 

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