Number 3 and 4 Cylinder Performance

[Samelak]

I had no spark coming from my number 4 cylinder and when I got home, I found the spark plug came loose from the coil. I probably drove a good 10 miles in this condition. After plugging everything back in, I felt the header get warm again. But the 3 and 4, which share the same coil, are not getting as hot as the rest. Is it possible I may have weakened my coil from driving with it disconnected? I do remember hearing a crackling noise which turned out the coil was arcing against my steel braided oil cooler line. The coils are Dyna. Any thoughts?

[steve murdoch icoa #5322]

I would not think there is any damage to the coil.
If the plug lead came loose is it possible the ground wire is loose as well?

[Larry Zimmer]

Or, did a 'carbon' path develop across the face of the coil. Clean the coil with some brake cleaner or electronic cleaner just to be certain. Also, that there is no damage anywhere to the wiring/boots, etc. that would promote surface arcing even though everything is connected.

[6Pipes]

Perhaps the plugs are fowled. You could try swapping them to different cylinders.

[Mike Nixon]

Sorry for showing up late to this thread but just a 2 cent comment, if you don't mind. Ignition coils definitely get stresssed from an unbridgeable gap in the secondary. Dual output ignition coils are especially susceptible and will tend to arc internally to complete the circuit. Enough arcing and the insulation is worn away in one spot on the winding, makng if effectively fewer coils and thus reduced output. The thing to do is swap the existing coils around and see if the cooler head pipe follows the suspect coil.