I have a 1994 Cavalier with the 2.2L engine, 97K miles.
Recently it has started to knock & ping, and the fuel
economy has dropped 15-20%. No other symptoms present,
and no change in driving style/conditions.
I've been told it could either be a faulty EGR valve, or
a plugged catalytic converter. I changed the spark
plugs, no effect. Any thoughts ?
Thanks in advance...