1994 Mark VIII engine stutters at stoplight

Hello, I have a 1994 Lincoln Mark VIII and something has been making the yellow "CHECK ENGINE" light go on and off sporadically while the car is driven. When I start the car up, and put it into reverse, the engine does not run smoothly at all. It stutters and stutters, then when I drive it, it will stutter again when I come to a stoplight or stop sign. I have to put my foot on the accelerator (while the brake pedal is pushed) to keep the car from stuttering while I'm stopped. It stutters so much sometimes that the RPMs almost go down to only 200-300 and almost stalls out.

I got new spark plugs and new wires 5 months ago, and this problem seemed to happen before that too. I got an oil change, a new air filter and a new serpentine belt a week or two ago... yet this problem still persists.

What is causing this? Two auto mechanics so far can't figure it out.

Thanks
Stef

I had a similar problem with my crown victoria a year ago. Sometimes in EFI engines there is an idle air bypass valve, i know the MarkvIII has one, and i would start there. This solenoid is located is somewhere in the intake manifold, i'm to lazy to pop the hood and look in there. Anyway clean that valve with carburetor or brake cleaner, and put it back, i beleive that should fix the problem. in this link you can see the actual valve, but i don't know where is located in the mark.

http://www.fordfuelinjection.com/?p=39