97 mountaineer misfire

[derek54401]

97 mountaineer 5.0
5-speed, AWD

the mountaineer has a horrible misfire which usually occurs after driving through a puddle or any rain covered road. It does not go away immediately after the vehicle has had time to dry out, the problem can persist for hours or even days.

I removed the wheel and used a spray bottle to wet the plug wires. when wet, there is a noticeable spark between several of the wires. Also, I can see a spark arcing from underneath the spark plug boot to the head.

The wires have been replaced twice to try and fix the problem, once with motorcraft wires and another time with napa belden wires.

plugs are autolite double platinum and are correctly gapped.

Any suggestions as to what could be causing this strange arcing and misfire?


Derek

 

[jremington59]

The wires can't be worth much. If those wires are new I'd be taking them back. I've used Beldens before and didn't have any problem with them. They aren't the best quality wire, but they shouldn't be shorting when they are new.

Do you have a mud flap on the inside of the wheel well?

 

[derek54401]

had a new set of motorcraft wires on there as well, did not make any difference. I do have the inner fender shields installed.

is there any way the firing voltage could be too high, causing them to short out?

 

[jremington59]

Are you spraying the coilpack when you mist them with water? The elec has to be coming from somewhere other than the new wires.

 

[tjf339280]

I am having a similar issue after driving through the car wash today my car stalled then CEL came on showing #6 misfire....replacing wires and plugs tomorrow, I have a 97 5.0L mounty, what do y'all recommend for wire/plug combo...Im thinking duralast wires with the AP 104 Single Platinum...

 

[matt0248]

Are you using dielectric grease on the plug wires?

Just a ithought. In theory double platinum plugs take more kV to fire that a standard plug. Therefore if the ignition coil is weak and cannot produce enough kV to fire the plug it will "leak" to ground through and around the plug boot. Especially when wet.

 

[derek54401]

got napa to swap out the wires for another new set, which fixed the problem. brand new wires giving problems, go figure. you're probably right that the coils aren't producing as much voltage as they were when new, so that may be a contributing factor.

 

[derek54401]

i'd tend to steer away from autozone house brand wires. if you want to get parts store wires, get the carquest wires. made by prestolite, same as the motorcrafts. autolite plugs are a great choice.

 

[MR SCARY]

Mine was shorting out to the steel sleeves on the boots.I removed the sleeves and never had a problem and have not burned the boots