Engine Mechanical

WARNING: This page is about a different car, the 2003 Oldsmobile Aurora. However, it is still accessible from the selected car via links, so may be relevant.

Check and inspect engine mechanical:

Check cylinder compression. See ENGINE COMPRESSION TEST under MECHANICAL INSPECTION under PRELIMINARY INSPECTION & ADJUSTMENTS in BASIC DIAGNOSTIC PROCEDURES - 4.0L AURORA article.
Check for sticking or leaking valves, worn camshaft lobes, valve timing and worn rocker arms, broken valve springs, leaking valve seals and excessive oil in the combustion chamber. Check for leaking valve seals. See appropriate article in ENGINES.

Check for incorrect basic engine parts. Check the camshaft, cylinder heads, pistons, etc. See appropriate article in ENGINES.