I have an 03 Z with 140K miles on it.

The car has performed flawlessly until last night. I went out to the driveway to pull it into the garage and when I cranked it, I got a loud clack-clack-clack-clack sound that (over a 25 second span) softened into steady tap. The Tap does increase with revs.

I immediately checked the oil as I assumed it was some type of knock. Car is fine on oil, even added a half quart to make sure I was within the marks.

This morning I crank to go to work and its the same thing. This time a check engine light comes on. P0304 misfire to cylinder 4. Car drove fine to work and I couldn't even hear the tap anymore. I recranked it (car warm) and no clack or tap.

I want to think that this is more than simply a misfire cylinder because of the terrible clack-clack-clack sound.

My next step is to swap a coil to cylinder 4 to see if the code changes to another cylinder. If it doesn't I guess I will change the plug.

Does anyone have any other thoughts? I have read things such as timing chain and valve tapping/needing adjustment? And if it was the valves needing adjustment, I have read people saying both that you can't adjust our valves and others say you can?

HELP PLEASE??

 

TTT any thoughts guys?