I'm getting a slight shake or miss at idle and mechanic says the car will be running fine as far as air/fuel ratio then suddenly turns rich.
Replaced distributor, cap, rotor, pcv valve, fuel filter. Can't figure out why it would go rich and star to miss. Not noticeable past idle. Any ideas?
Thanks in advance.
Frank

 

have you checked your O2 sensor operation?

 

Any more ideas?