I have a '99 Pontiac Grand Prix. I think the upper intake manifold plenum is bad and has fouled out my sparkplugs. But, I was told this could also lock the engine up. What is the best way to go about this problem?

Jeff

 

Apparently early 3800 series II motors like the 1999 had plastic intake manifolds that were prone to problems much like the ones you've experienced. I bought my 1999 in 2002 as a lease return and it has the aluminum manifold. My guess is GM may have replaced either as a recall or to cover their *** on the lease vehicles.