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Normal compression on 4.6?

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Old 04-26-2009, 08:26 PM
CAMOBRUTE750i CAMOBRUTE750i is offline
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Normal compression on 4.6?

engine has 250,000 miles, but just had a tune up around late January or early February...now it's misfiring on #4 & #7, can't figure it out?? Replaced the plugs just to make sure but still doing it?? Checked the compression and it has 125 psi on #7...is that normal? What could be the problem...valves?
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Old 04-26-2009, 08:28 PM
CAMOBRUTE750i CAMOBRUTE750i is offline
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1998 F-150 Triton 4.6L
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Old 04-27-2009, 07:26 AM
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125 psi is good compression-I've seen from 105-165 psi on 4.6L's in the past.
The big question is-what did you get on ALL of the cylinders?
JL
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Old 04-27-2009, 09:14 AM
CAMOBRUTE750i CAMOBRUTE750i is offline
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I can't figure it out...I've checked the codes one time and it said #4 & #7 were misfiring...cleared the codes and it set the check engine light off again with the same exact codes...it doesn't jerk and shake all the time...it goes and comes but keeps giving the same codes...coil packs are arcing fine on the cylinders...what do you think it could be?
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Old 04-27-2009, 09:23 AM
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Originally Posted by CAMOBRUTE750i View Post
I can't figure it out...I've checked the codes one time and it said #4 & #7 were misfiring...cleared the codes and it set the check engine light off again with the same exact codes...it doesn't jerk and shake all the time...it goes and comes but keeps giving the same codes...coil packs are arcing fine on the cylinders...what do you think it could be?
Move the COP's to other cylinders and see if the codes follow.
JL
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Old 04-28-2009, 05:34 PM
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Sounds like either bad coils or coil boots. Do as Johnny sais, move those two coild to different cylinders and see if the codes follow.
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