High RPMs on start

1990 Jeep Cherokee, 4X4, 4.0L.

As soon as the Jeep starts the RPMs jump to 3k-4k. and will stay there.
If I push on the throttle linkage I can get the rpms close to normal.
As soon as I let off on the linkage, the rpms raise high again.
**on edit** I also removed the vaccuum line from the MAP sensor to the TB and the RPMs
dropped almost to where it would stall, but would go right back to 3000 when I put it back on.

The accelerator cable is new.

I am thinking that it is the IAC or carbon build up on the butterfly of the throttle body.
My son told me that the rpms have been surging lately (between 700-1500).

What do you guys think?

Mike

This issue has been resolved. It turns out that it was the accelerator cable (aftermarket from Dorman).

Here is how I troubleshot it:
1) disconnected the the metal linkage arm from the throttle valve
2) started the vehicle (it idled normal). turned it back off
3) reconnected the metal linkage and disconnected the accelerator cable
4) started the vehicle (it idled normal). Shut it back off.
5) Went to JEEP dealer and ordered part 53005245 (short cable)
6) installed cable and went on my merry way