Where's Rubo when you need him? <img src="/forums/images/graemlins/smile.gif" alt="" />

I could see that chain of events happening, since the cylinder head cover can be pretty well isolated, sitting on its rubber gaskets, connected to ground by vacuum lines. <img src="/forums/images/graemlins/pfft.gif" alt="" />

That said, internet diagnosis can be difficult... especially when it comes to root cause. We can talk about specific symptoms, tho -- if you think you have carbon-coated your combustion chambers (pinging early, down on power, carbon on the plugs, etc.), try feeding your motor some water. A little at a time is the key -- too much and you'll hydrolock, which is BAD -- so be careful.

Generally, what I do is take a jar of water and disconnect a small vacuum hose and let the running motor suck off the surface of the water (don't just drop the hose in the water). Use one hand to turn the linkage at the throttle body to get off-idle, and listen to the note of the engine. It will struggle a bit as you suck in water -- when you hear that, lift the hose (stop sucking water) and let it smooth out. Lather, rinse, and repeat... Lather, rinse, and repeat. Run a quart of water through the combustion chambers over the space of 15 minutes, and you'll effectively steam-clean the head and piston tops. Those of you who have blown a head gasket (literally) have seen the effects, where the piston with coolant leaked into it is clean and shiny, when compared to the other pistons that have normal combustion deposits in them.

If done carefully, this won't hurt your engine, and might help.... but it should eliminate the possibility of carbon-coated combustion chambers, and the resulting rise in compression ratio with pre-ignition.

Randii