1989 930, 34k miles, stock.
There is a tapping noise at idle similar to loose rocker arm type tapping in a pushrod motor. It is not present at cold start or fully warmed up, just from about 5 minutes to 20 minutes of running. Seems to be coming from the top center of the engine but very hard to tell. Engine has had recent service with new plugs, valve adjustment etc. Leak down #'s are very good at 1-2% each cylinder. Noise was present before the service. My shop has not been able to determine cause. Engine runs great otherwise so am reluctant to tear into it looking for cause without at least a theory.
Welcome ideas on the possible cause. Thanks.
