Discolored ignition coil

[revvhappy]

2005 V8 with 124k miles. I just finished changing my spark plugs and I'm fairly sure that the original plugs were still in the engine. All went well on the driver side, but then I found this on the passenger side bank (#4 cylinder, 2nd from front). This was the only plug that seemed less tight than the others. It seemed to be functioning correctly and the inside of the coil boot was clean.

Any ideas about a cause?

 

[blackoutt]

This can happen when the grommet that seals the coil to the valve cover has a leak. The electrical path is still clean all the way through to the spark plug boot/spark plug terminal so you wouldn't notice it until it broke that seal. I would replace it because it's ugly but it's most likely fine to clean and reuse. Just make sure the mating surfaces aren't damaged and free from debris or that they haven't taken a set to an odd form causing the leak.

The other common cause which you've eluded to is spark plug not to correct torque, this usually has noticeable effects and eventually cooks the coil though.

 

[revvhappy]

Thank you. I'll clean it up and keep using it until there's a malfunction.

 

[snowboardwcu]

This can happen when the grommet that seals the coil to the valve cover has a leak.

look at the far left coil though, it doesn't even have a grommet if i'm seeing right.

not to correct torque

would be my vote. i did mine a few months back, cyl5 had some discoloration. no where near this bad. plug looked similar. no issues with it so at the end of the day, i think blackoutt has the right answer.

 

[ben550]

When I changed my plugs, I found two coils which looked the same as yours. One of them was actually cracking and splitting... I replaced the cracked coil and reinstalled the others. I found that the plugs under the discolored coils were not torqued correctly. One was very loose. I torqued the new plugs correctly and installed the coils. No problems. If its not cracked, re-use it and you should have no issues.

 

[revvhappy]

Good observation about the grommet, it stayed on the valve cover when I removed that coil. As I backed out of the driveway for a test ride I noticed something in the driveway... turned out to be a grommet that had fallen off the left side when I wasn't looking. They are all in place now.