misfire
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Elder User
Joined: Nov 2010
Posts: 946
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From: Needville, TX
misfire
I have a misfire on my truck and haven't thrown a code yet. My scangauge picked up a p0304 code which is cylinder 4. I picked up a new COP and replaced what i thought was cylinder 4. (All the way in the back on the driver side.) After replacing it i still have a miss.... Doing a little research...i think i got some bad information...i think #4 is in the back on the passenger side...Just looking for a little confirmation from the brotherhood. Thanks 
Elder User
Joined: Feb 2006
Posts: 545
Likes: 5
From: FL
Some of the reasons for misfire :
1-Bad spark plug
2-Arcing thru rubber boot
3-mulfunctioning COP
4-Wiring/electrical plug contacts
5-mulfunctioning Injector
You can install a brand new spark plug(motocraft) + rubber boot + review wiring/plugs to see if misfire is still there . If it is still there , then you can swap two COP coils (for example with #3 coil and #4) and check with the scangauge , is the error code still at #4 or moved to #3 ? . If the error code is still at #4 , then may be you need to start doing some diagnostics on injector #4 . Remember , after installing new spark plug and/or swapping COPs , you need to clear codes by either thru scangauge or unhooking battery (-) terminal . You can also try a good quality injector cleaner .
Good luck,
PS. #4 should be on very back at passenger side,
1-Bad spark plug
2-Arcing thru rubber boot
3-mulfunctioning COP
4-Wiring/electrical plug contacts
5-mulfunctioning Injector
You can install a brand new spark plug(motocraft) + rubber boot + review wiring/plugs to see if misfire is still there . If it is still there , then you can swap two COP coils (for example with #3 coil and #4) and check with the scangauge , is the error code still at #4 or moved to #3 ? . If the error code is still at #4 , then may be you need to start doing some diagnostics on injector #4 . Remember , after installing new spark plug and/or swapping COPs , you need to clear codes by either thru scangauge or unhooking battery (-) terminal . You can also try a good quality injector cleaner .
Good luck,
PS. #4 should be on very back at passenger side,
FTE Leadership Emeritus
Joined: Sep 2000
Posts: 23,174
Likes: 1,678
From: Stephensville WI
Stop. Don't buy any more parts.
Move the new COP to the offending cylinder and swap the spark plug with another cylinder. If the misfire goes away it is the COP. If it moves to #3 it is the spark plug. If it stays at #4, it is something else.
Move the new COP to the offending cylinder and swap the spark plug with another cylinder. If the misfire goes away it is the COP. If it moves to #3 it is the spark plug. If it stays at #4, it is something else.
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Elder User
Joined: Nov 2010
Posts: 946
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From: Needville, TX
Thanks for the information guys, I left the new cop on number 8 and installed the one I took off of number 8 on to number 4 and it fix my problem . Nothing worse than trying to pull 10000 pounds on 7 cylinders lol.
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