Can you look at your spark plugs and tell if you have a bad coil? I am replacing both my plugs and the coilpacks in the next few days and was just curious if by looking at a plug I could tell it had a bad coil in it. Hopefully this will take care of my check engine light, if not then it will be time to replace the knock sensor...

 

did you have a misfire code or something or are you just replacing your coils?...Fouled spark plugs could mean a number of things... but it is safe to say that if one of the plugs is blackened that there is likely a problem with the coil not firing. But if you have a check engine light you should already know or have an idea of what the problem is. (it's when you don't have a check engine light or codes that it sucks!!)... btw... what is the problem? is the light just on or do you have problems to go with it?

 

I do have a misfire code. Also at times my car will shake as if it is going to stall around 1500 rpms when I am just cruising around. I am hoping to fix this and restore some performance to my maxima.

 

How old are your plugs? What do your plugs look like? To test the coils just take a plug you know to be good and go around to each coil individualy.

 

My plugs are NGK copper plugs and they have about 25k on them so I figured I would go ahead and swap them out since I am doing coils.

 

I've never heard of any direct correlation between spark plug appearance and coil problems, but what 3d man said is probably a good bet.

My coilpack problems have always manifest themselves at higher throttle positions and RPM, but that's not to say they couldn't appear under different conditions.