Join the Car Talk Community!

Discussion Rules

Welcome to the Car Talk Community!

Want to ask a question or join the discussion? Great! Join now.

Sign In Register

What causes a car engine to idle rough and miss?

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


  • edited October 2009
    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.
  • edited October 2009
    When was the last time the fuel filter was replaced.
  • edited October 2009
    Compression test.
    Check for leaky EGR valve.
  • edited October 2009
    Look for vacuum leak
This discussion has been closed.