Frankenvette

Have not done anything to the engine recently, yet my vette is riding rough. I can feel it surge while driving and sort of hear what sounds like a small backfire when letting up on the gas. I double checked my sparkplug wires to make sure they are all connected tight. The plugs, wires, rotor, cap, gas filter and air filter all have less than 3,000 miles on them with little usage over the last year. No emissions on the car to get in the way and the timing was set while on the dyno last year. This problem just started out of nowhere. Car was running smooth last month. No known reason things should have changed. Also, I noticed that the tach is bouncing, and it has not done that before either. Could a failing coil cause this surging(bucking) and rough idle? I think the coil is very old. Any other thoughts?

vettfixr

OK, don't beat me up too bad on this but I had the same problem on an (oh God help me now) Opel Kadette. It turned out that the vacuum advance went bad and stuck in the full advance position. Try disconnecting the vacuum advance from the carb and hooking it up to a full vacuum port at idle. If the engine speeds up from the advance and slows down when you pull the hose the advance is working. If it doesn't you probably have a bad vacuum advance can. Usually surging, backfiring, etc. are ignition related. Good luck.


[Modified by vettfixr, 7:50 PM 3/27/2003]

Dk Met Grn 80 L82

Thats a good tip for checking the vacuum advance. I have suspected problems with mine, but don't have a timing light yet and I was trying to figure out how I could test the vacuum advance working. I'm gonna try it this weekend. :jester