I just wrapped up the engine refurbish on my 16 yr.old neighbor's first car Fri. night. It started fine and idles smoothly - except - it's doing something I have not encountered before.

It idles and revs as it should for maybe 10 seconds or so, then there is an aubible click in the engine area followed by another click maybe a second later, as if something is switching off and back on again or vice versa. Following the second click, there is also a slight but noticeable momentary engine RPM increase before settling back to normal running. This process then repeats.

Any thoughts on this anomaly? All dash lights work normally ... it will need a battery replacement - had to charge it after sitting while doing engine work.

Jim