[esrman]

I had the same problem.

It was a broken rocker arm stud.

A trip to the junk yard yielded a used one and that cured it for about a week!

Then the same rocker arm came loose,yes I torqued it.

Torqueing again solved the problem,I hope.

its been 2 weeks now.

Take a cylinder compression chek.

The bad stud or rocker arm will show,as that cylinder will have absolutely NO compression.

Another clue would be that it des not idle smoothly.