Possible C.o.p. Problem

[lonestar1]

Gentlemen, have a 2002 gt with moderately rough running engine. Also my mileage has dropped off in the last couple of weeks. At about 1500 revs is runs as if it were missing just enough to be annoying. Still has great power and catches rubber into second with the auto.

Wondering if it could be a COP. Hasn't thrown a code or anything. Can the COPS go partially out or do they just die. Is it wise to get a new COP and just start swapping it out with the originals and try to find a problem or can they be checked. Have about 165K on the engine and just replaced the IAC. Throttle body and MAF are clean and I use seafoam about every 7500 miles. Plugs are irridium and about 25K miles on them.

Any ideas would be appreciated.
Lonestar

 

[wmburns]

Start first with the basic stuff. Is there any moisture in the spark plug wells? If so, this will ground out the spark causing misfire. If allowed to continue, this will damage the COP insulator. Once damaged the misfire will continue. It's much cheaper to replace just the COP boot instead of the entire COP.

Autozone (Duralast) makes a very affordable set.

Part Number: 90003​

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Alternate Part Number: CP83​

http://www.autozone.com/autozone/pa...N-jhcm1Z8gcsm?itemIdentifier=991088_406280_0_

 

[lonestar1]

Start first with the basic stuff. Is there any moisture in the spark plug wells? If so, this will ground out the spark causing misfire. If allowed to continue, this will damage the COP insulator. Once damaged the misfire will continue. It's much cheaper to replace just the COP boot instead of the entire COP.

Autozone (Duralast) makes a very affordable set.

 

[lonestar1]

Don't think I have any moisture problems, it's possible, but I don't see any evidence of it. I guess then that a COP would fail completely rather than partially?
Thanks, Lonestar

 

[1lugloose]

Just posted my own thread with a similar issue. Are you having this issue constantly from start up or only during or after the engine warms up?

 

[lonestar1]

Just posted my own thread with a similar issue. Are you having this issue constantly from start up or only during or after the engine warms up?

It is mostly constant, but not noticible unless I'm cruising about 1500 revs. More of an irriitation as driving in Houston has that speed a lot. Mileage drop off does hurt somewhat. Just don't know how to trace problem and fix it.
Lonestar1

 

[wmburns]

Other things to check.

• Dirty MAF. Clean using only a product designed for the job.
• Under drive pulleys. Sometime UD pulleys can cause an unstable CKP signal
• incorrectly torqued crank damper bolt or out of round crank damper.
• excessive EGR flow. Does disconnecting and plugging the EGR valve vacuum line improve symptoms. Check the DPFE sensor for leaks in the rubber vacuum hoses.
• Clogged fuel filter.
• leaking/disconnected FRPS intake vacuum reference line.
• moisture in the spark plug wells. Reread the part about how moisture damages the insulator boot.
• vacuum leak
• exhaust leak

 

[95Vert383AOD]

Issue i had when i first got my Towncar is that the previous owner didn't install the angled COP rubber boots correctly. If they aren't clocked right when you put them in the heat will warp the rubber allowing moisture in. Personally when installing mine i add a light amount of grease to the coil boot where it meets the motor.

 

[evolucion311]

Let me know if you need a set of COPs. I replaced all of mine chasing a misfire that ended up being a burned exhaust valve. I've got like 10 of them. They are just laying around and I can help you out for a LOT less than new.

 

[evolucion311]

A second thought.... why are you running iridium plugs? Unless you've got a good reason not to (like nitrous, supercharger, etc) you should be using plain-jane Motorcraft platinum plugs.

Replace with OEM plugs and COP boots, reset computer, try again. Rock auto dot com has great prices on parts, I've never found anyone cheaper.