my 85 740 runs great except for a rough idle that doesn't go away...it has never stalled on me but it has a pretty rough idle and has recently started to have a fluctuating idle and smells rich when cold ...idle smooths out when I accelerate..but as soon as I am stopped the rough idle comes back..warm or cold.. I don't have $$ to take it to a mechanic to diagnose it, so any help to point me in the right direction would be great

 

Sounds like a low speed misfire. Start with the basics: check plugs, wires, rotor, cap. Look for a vacuum leak, check all the little hoses around the intake, listen for hissing noises. For a start...

 

Is this a California car with EGR? If so, does the car smooth out when you disconnect the EGR Vacumn Controller plug?