This is for a 1991 Chevy G10 Van with a 5.7L (350cu.in.) engine.

The engine has been missing at an idle. The warmer it gets the more it misses.

The number 1 and 3 spark plugs are oil fouled.

The spark plug heat shield for the number 1 and 3 plugs is missing. I bought this van 30,000 miles ago. I was told that this engine was new and only had 40,000 miles on it. The guy who sold me the van put the engine in himself.

The engine oil is clean.

I can't help thinking that the missing heat shields have something to do with the missing. Has anyone ever heard of a missing heat shield causing oil fouling and missing?