I have a 2004 Grand Cherokee with a 4.7L.  I have been having problems the past month with a high idle that won't go down. Dealer can't seem to fix.  I have had a new computer put in, air idle sensore replaced, as well as new spark plugs, fuel injectors cleaned, etc.  It is high in the morning first starting and very slow to come down to normal rpm range which is around 600rpm  After I drive for a while and put into drive is rev's up to about 1000rpm.  Way too high for a stock Jeep?  Any suggestions how to fix this problem.

thanks,  

check for leaky vaccume lines.  

Throttle Position Sensor? that would be my guess  

If it eventually idles down, maybe the PCM assumes low operating temp because of an Engine Coolant Temp sensor (ECT) problem. Maybe the thermostat is not working correctly and it really is operating cool. The temp is an input for the high idle protocol.

You stated that the "Idle Sensor" was replaced. There is not a sensor by that name. There is an Intake Air Temp sensor (IAT) and an Idle Air Control (IAC) motor. The IAC motor does get stuck and sometimes needs a little maintenance. They might have replaced the IAC. The Jeep would probably run really bad if the IAT were bad.

With a Manifold Pressure sensor (MAP), which you have, as opposed to a Mass Air Flow sensor (MAF), a vacuum leak can be interpreted by the PCM as throttle input (more air volume in the manifold). This could be why there are no DTCs in the computer to tell the boys at the dealer what's up so they don't have to guess.

There is a propane vacuum leak detector device that is used to detect vacuum leaks. Basically you spray a little propane around different areas of the intake manifold and if the idle bumps up, you found the leak. Ask the dealer to do this or take it to a shop. Any shop should have a propane vacuum leak detection device.