This car is a V8, always serviced Plugs and wires changed, O2 sensor changed, distributor new, premium gas used, injector cleaner used – still rough idle and miss Thanks! Any ideas? 1990 Cadillac 4.5 liter 99K

What causes a car engine to idle rough and miss?

budd2049 October 11, 2009, 5:20am 2

I’m assuming a new cap and rotor were part of the distributor replacement.

Has a compression check been performed? Perhaps one of the valves is burned or not sealing properly.