I have a 95 sedan deville. It is a great Cadilac except it seems to have a preignition firing problem. I have reset the timing, changed plugs, replaced the computer, replaced the EGR valve, replaced the throttle position sensor, and the gas filter and O2 sensors. I run premium gas as specified by GM.
What am I missing?
The car will not idle correctly (rough idle and then dies). Also the car will have a sudden idle increase that will reduce after a few moments.
When I try to pull an incline I lose power, and must idle up the hill.
However, most in town driving is fairly normal.
Does this sound familiar to anyone?
Mack

:welcome: Preignition? I assume you mean detonation (pinging or knocking), as preignition is usually fatal. Check for a vacuum leak or a malfunctioning EGR solenoid.