Worn distributor bushing, vacuum leak, worn camshaft lobe, sloppy timing chain, burned valve.
Burned valve will sound like an air compressor, and can be found with a cylinder leakage test.
Vacuum leak can be found by spraying water around the intake manifold gaskets.
Worn timing chain can be verified by removing the mechanical fuel pump block-off plate and pushing on the chain with a piece of coat hanger wire.
Worn distributor bushing can be verified by watching timing marks with a timing light. Timing will be erratic and marks will be bouncing all over.
Worn cam lobe / weak cylinder can be found with a cylinder power balance test.
Tuesday, June 16th, 2009 AT 4:08 PM