Throttle Actuator

Try cleaning the slide. When you take off the entire tubing that runs across the top of the engine from the air cleaner box and goes down into the manifold you will fine that you can look down right into the slide. What happens is as time passes, the slide developes it's own seal. So everytime you take your foot off the gas pedel, the slide closes and chokes the car out. The slide is made to allow just enough air into the engine at rest to keep the car idling. When the seal (carbon buildup) forms, it stops air from entering the engine at idle. Just take a clean rag and rap it around a pair of long needle-nose and spray a little gas on the rag. Once you clean it, let it dry for a few minutes and put everything back together before you start the car. If you go to the dealer , they are going to tell you you need a new slide $1800.00 . It might very well be the slide, but I suggest you try cleaning yours before changing it. Hope this helps