The best i have found is disconnect the battery and the #4 and #11(under hood) fuse, for about five minutes. Then connect all of them back up and start your car, let run until idle goes back to normal.
'95 Contour GL, zetec mtx, drop in K&N, exhaust res removed, 4 10" Kenwoods powered by 1000W Visonik amp, 4 5"x7"/6"x8" Visoniks