I have a 2005 Taurus SEL with 123K miles. The engine runs a little rough at idle and the tach jumps up and down about 50 RPM when the car is sitting still. It runs fine on the hiway and MPG is 29-30. I replaced plugs, had a smoke test run for vac leaks, (fixed one on PCV line), but no other leaks were found. I cleaned the throttle body and MAF sensor also and replaced the air filter. Does anyone have any other ideas? I have been told that a broken tooth on the cam syncronizer can cause this but it is not making any chirping noise.