I have a 2000 Ranger with a 3.0 flexi fuel. I keep getting a #6 missfire code and the engine will sometimes run really rough until I just get in to it and floor it, then it runs fine again for a while. I have changed the plugs, wires, coil pack and the injector and it still does it. I have also inspected the valve springs and they dont look broken in any way. I also have a tapping noise that seems to be a lifter noise but not sure and that tapping noise is loud sometimes and others you can barely hear it. I was going to use a bore scope next to take a look at the backside of the valves to see if there is any buildup but had been told there was a TSB stating that the vavle guides could make the valves stick but hadnt found anything like that. Any thoughts?

 

Experiencing any coolant loss ?
Quote:
that tapping noise is loud sometimes and others you can barely hear it

Bad head gasket ?

 

Or lower intake to head gasket leak.......With the engine running, try spraying some carb cleaner where the lower intake meets the head (driver's side bank).
If you get a change in RPM, then you have found your leak.

 

No coolant loss and it doesnt use any oil at all and it doesnt smoke at all. I will try the gasket test tonight when I get home.