Car isn't running right.
 

I just replaced the IAC in my car. After I replaced it, when I rev the car up, it takes 3 or 4 seconds for it to rev back down. When I drive the car, I have to wait before for the RPM's to drop before I shift!
Another problem, not related to the above, is that my tach won't drop below 4000 RPM's. When I get on it, it will move up some and then stop back at 4000.

Any Help?????

In terms of the IAC valve, I just replaced mine on my 1993 GT: Make sure that the part number is correct (check your local part store) sometimes between years the parts may fluctuate a bit. Also check the electrical connections for rust or damaged wires which may short out the signal between the unit and the EEC.
My 2 cents.
The RPM dial coil (behind the instrument panel) may be damaged, but I'm just speculating. I hope someone else help you with this. Sorry! good luck!
fongo