P0308 Cyl 8 misfire-where to start?

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Steve Krusich

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Feb 21, 2006
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Just tonight my 07 V8 with 62K started to stumble. The code is "P0308, cyl 8 misfire". What are the odds as I start to guess? Should I start with the ignition coil...the plug...the injector....or somewhere else?



It is cold here but it has to be right. Thanks
 
Do something simple first. Swap out an ignition wire and reset the code. If it comes back to CYL 8, then it is not the wire. Then swap the spark plug and reset the codes. If it comes back still on CLY 8, you have isolated it a bit more. If it moves to whatever cylinder you moved the items to, then it was the plug or wire or whatever you last swapped...
 
That's a logical suggestion... Why didn't I think of that? I will do that.



What do you think is the highest probability part? It seems to me that it is unlikely for the wire to fail. To me, the coil or plug seems to be a more likely culprit.



What is your bet?
 
Recently, there have been a fair amount of coils going bad compared to the norm. However, to help confirm your issue. I would swap a wire and a plug at the same time. If it moves to the other cylinder, then simply replace the plugs and wires as it is probably time. If it does not move, it is probably a coil issue.



Could be a gasket or vacuum issue but not a high likelihood compared to the normal issues with a cylinder misfire..
 
From all I have read I am fearful of trying to remove the spark plug on this 2007 4.6 V8. Others have said the plug is very likely to break off and then I would have real trouble.



What is the recommended replacement plug for the 4.6 V8?
 
Last edited by a moderator:
In the end, most have gone with OEM plugs as many for some reason just don't seem to well in the Trac.



Go with just one of the wires for now and see what happens, don't forget to reset it...
 
I have changed the plugs in all 4 of my Gen 1 V6's without problem. What is your opinion or experience with the difficulty in changing the Gen 2 V8 plugs?
 
Looks like the story ends by my discovery of water in the plug recess. I was changing the ignition coils between cylinders to determine if it was the coil or the plug and discovered the water/ice. It must have been in there for several months because the last time I rinsed the engine area was in the fall.



Anyway....problem solved. Thanks Coastiejoe for your advice.
 

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