I have a 2000 Jeep Cherokee Sportwith the 4L 6CYL with about 160K miles. Recently I've had an increase in a the randomness of occurrence which lately has been more frequent. I'll start the engine and it races at high idle.The problem is the engine runs fine for days or weeks at a time. Then one day I'll start the engine and again, it races at high idle.Re-starting does nothing. I can drive and make several stops and sometimes when I re-start, it again races at high idle. I have no CODES. Can any help suggest what I can check or replace.

 

EGR Valve, I've ran into the same problem with my saturn and it fixed the problem. Also run some sea foam in the gas tank with a full tank to clean out the gas lines and injectors.

 

sounds like the IAC is sticking, you can try to clean it, my 99 had the same problem but mine was that the pintle screw that goes into the stepper motor was stripped out so I had to replace it. Also if it hangs up after you let of the gas also check/clean the throttle blade carbon build up will cause it to hang up

 

AFAIK 4.0s did not have an EGR after '90