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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #1 ·
I just changed spark plugs ~2500 miles ago due to a misfire code and yes they were worn fairly bad. Any ideas why it keeps doing this?
 

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Premium Member
2005 Jeep Grand Cherokee
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2,807 Posts
How many miles on the car? Do you feel the misfire, if so when/how are you driving, vehicle rpms, are you throttle to the floor or idling, etc?
 

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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #3 ·
Thanks for the reply my first one! All cheering aside yes my jeep shakes pretty bad at an idle. I changed the spark plugs and it stopped and just noticed today had the code read and sure enough it was it. Cylinder 4 this time. It has 137k on the whole thing. Could it have been my cheap nature at the time purchasing cheap plugs?
 

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Project Six Shooter V2 / ROUSH Prototype Tech
2000 Grand Cherokee 4.0 w/Select-trac
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9,250 Posts
Thanks for the reply my first one! All cheering aside yes my jeep shakes pretty bad at an idle. I changed the spark plugs and it stopped and just noticed today had the code read and sure enough it was it. Cylinder 4 this time. It has 137k on the whole thing. Could it have been my cheap nature at the time purchasing cheap plugs?

possibly the cheap plugs, but what did you buy? my next guess is that it could be a bad coil, try to swap them around and see if the miss fire moves to a new cylinder.
 

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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #5 ·
I'll try it when I get off work tomorrow. Funny thing you say the oil cause I just changed my oil Sunday. I bout the auto lite 5224. They were a whopping $1.85 ea.
 

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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #6 ·
Wow I misread oil for coil. My phone isn't the best for forum posting.
 

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Project Six Shooter V2 / ROUSH Prototype Tech
2000 Grand Cherokee 4.0 w/Select-trac
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9,250 Posts
Wow I misread oil for coil. My phone isn't the best for forum posting.
that's ok, those auto lites should be copper core, and may not be the problem
 

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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #8 ·
Yes they are copper core. I know they are all set right because I did it myself.
 

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Premium Member
2005 Jeep Grand Cherokee
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2,807 Posts
Chrysler products do NOT like autolites. But if it was doing it before I don't suspect that is the issue. I have seen valve guide issues cause a misfire at idle. That repair is likely going to be a remain cylinder head.

For a misfire you need to test for spark, fuel, and compression. Swap a coil and plug and injector to different cylinders and see if the code follows to one of those. If it stays on cyl 4 then you need to do a leak down test on that cylinder and go from there.
 

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Project Six Shooter V2 / ROUSH Prototype Tech
2000 Grand Cherokee 4.0 w/Select-trac
Joined
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9,250 Posts
Chrysler products do NOT like autolites. But if it was doing it before I don't suspect that is the issue. I have seen valve guide issues cause a misfire at idle. That repair is likely going to be a remain cylinder head.

For a misfire you need to test for spark, fuel, and compression. Swap a coil and plug and injector to different cylinders and see if the code follows to one of those. If it stays on cyl 4 then you need to do a leak down test on that cylinder and go from there.

not true on the plugs, im running autolite xp iridiums and have had no problems
 

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2006 Jeep WK 3.7l
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19 Posts
Discussion Starter · #11 ·
I'll try using everybody's suggestions today after work. :thumbsup:
 
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