Starting about 8 months ago, I had an erratic misfire. It got more frequent, and eventually the check engine light came on. Took it to the local parts store where they hooked up the diagnostic reader. It showed cylinder 2 misfire. I pulled the #2 plug and found it covered in corrosion and gunk. (This is the boot side, mind you... cylinder side looked fine. These plugs were put in about 35k miles earlier.) So, I replaced the plug and wire, taking care to use anti-seize and boot grease, and checked the neighboring plugs. All looked well, and she ran perfectly thereafter... for about 6 months.

Two months ago, the exact same sequence repeated itself. Erratic then steady misfire. Diagnostic reader showed cylinder 2 misfire. Pulled the plug, only to find this 6-month old plug covered in corrosion like it had been in salt water for years. Replaced the plug (coating liberally with anti-seize this time) and plug wire. Again, checked neighboring plugs and found no problems. All was well again... until now.

Exact same scenario is now presenting itself for the third time. I haven't pulled the plug yet, but I fully expect to find the same problem.

No other plugs show signs of this corrosion, and there are no readily visible coolant or other leaks in the vicinity.

 

Try changing the cop?

 

Look real close for any possibility of coolant/water leak anywhere around that cylinder's plug well.
It it has repeated the same way, you have to be able to see the signs of what is causing it.
Is it traveling on a hose from some other location?

 

I don't have the COP setup... there are two coils, one on each side of the engine, each feeding 4 cylinders.

 

I've looked, but possibly not closely enough. I'll definitely give it another peek.

The corrosion covered the entire top side of the plug, everything outside the cylinder and including way up in the boot, to the point where the plug and wire connect. Pretty clear that's where the actual loss of conductivity is happening.

Any other clues? Thanks, and keep 'em coming, please...

 

Nah, ain't no stumper. Lower intake gaskets are leaking. They usually don't show themselves except when the engine is cold - pressure test the cooling system if you can with the engine cold, you'll see it. They typically leak at the corners of the intake.

 

i have been having the same trouble...i had mine checked and it said #8 cylinder is misfiring...i just replaced plugs and wires last year but a couple plugs were horrible...replacing them didnt help...i guess i will try new plug wires again and see if that works...im not sure if it could be coils or not...my truck is running fine until it warms up and then the CEL starts flashing..when it starts flashing the truck barely will run....

 

So what's the easiest fix here? Can I simply tighten something down, or does the gasket have to be replaced? Sounds like a not-so-fun project.

 

The gaskets need to be replaced. Sorry.