Vehicle: '94 GrandMarquis 4.6L 34k miles
What I have already done: New plugs and wires. New idle air control valve
Problem: I recently bought this car for my work car. Put around a hundred miles a day on it. It has intermittent rough idle and usually about once a day it will stall. When it is idling smooth you can't tell the engine is running and it has no other problems but sometimes it idles rough and surges... especially with the a/c off.
Turn off the a/c and come to a stop and it idles smooth as glass for about a ten count then falls off to a rough idle with surging. Whole car shakes as it surges but it never goes above a high idle rpm. Ten minutes later it is idling smooth as glass again. This is driving me nuts!!!
Parts replacement (above) had 0 effect on the problem
Any ideas?
Steve B.