Worn or loose rocker arms

The rocker arm bearing end caps and/or needle bearings should be intact within the rocker arm assembly.

Replace the valve rocker arms, as required.

Worn or bent pushrods

Stuck valves

Carbon buildup on the valve stem can cause the valve not to close properly.

Repair or replace, as required.

Excessively worn or mis-aligned timing chain

Replace the timing chain and sprockets, as required.

Worn camshaft lobes

Replace the camshaft and valve lifters.

Sticking lifters

Replace, as required.

Improper operation of the active fuel management system

Inspect the system for proper operation.

Refer to Diagnostic Starting Point - Engine Mechanical .