Engine Performance problem
1997 Chevy Suburban V8 Four Wheel Drive Automatic 136000 miles
Plug has been replaced and does have spark. Compression is 150+ and the cylinder is getting fuel.
After running for a short time the plug fouls and the engine misses? Possibly a manifold or head gasket leak?
Intake manifold gasket, not head. Not likely anyways.
Have seen intake gasket sucked in on #6 port allowing vaccum leak internally, remove pcv valve from valve cover and check for vaccum at gromment on valve cover. With pcv valve out lay finger over gromment and feel for suction.