hane a 1986 928 had to get the top end rebuilt due the water pump going out and devestating the engine.anyway engine is all back together new valves,tensioner the works now the mec/cant get the car to hold an idle and he seems at the point where he is ready to give up.what could it be?/

 

Hello Angelo - welcome to the 928 Forum.

My guess, based on the limited data you have available, would be that the cams were not properly aligned when installing the new timing belt, resulting in off-sync valve operation.

Anyone else?