This is a follow up to my original thread: COP Test, but I felt it worth listing new.

After hosing out engine compartment I developed major misfiring. Here is the "weakest link" I discoverd was dreating the problem:

1) Spark plugs are fine
2) COPs are fine (although possible, I thought it unlikely that water would actually penetrate these sealed plastic components)

The problem is the connection between the COP and the spring. Remove the rubber boot from the COP and gently twist and pull the spring out of the COP (on a few of mine the spring nearly fell out!) The connector inside the plastic housing was corroded/oxidized from electrolysis probaly caused by moisture and lack of a good tight fitting to begin with. I took some emory cloth and a small file and cleaned them. THen I sprayed electric contact cleaner on them. Next I slighly crushed the end of the spring to ensure a tighter fit.

Voila! Truck idles and runs better than it ever has!!

I can't say that this is going to solve everyones misfiring problems, but I bet there have been a s--tload of new COPs purchased unnecessarily. It didn't cost me anything...give it a shot.

By the way, AutoZone will let you take the OBDII scanner home for FREE! (have to leave a refundable deposit)


I have included a couple of blurry photos, hope they and this thread help.


Many Thanks to FTE, Racerguy, and Autozone.