i recently bought a 2004 grand cherokee for cheep and it is having idleing problems, ideal idle is around 700- 800 rpm, but when i start it it goes up to 400 and then goes straight to 0 the only way i keep it running is if i give it gas and keep the rpms up myself. btw i have changed the air filter, fuel filter, the heated O2 sensor and right now im thinking cleaning the injectors.

 

that and you might want to take a look at the idle air control valve on the throttle body, its the piece that has 4 screws on the passenger side, it might need some cleaning...

that could help another thing you might want to try is some Seafoam, depending on the mileage you might want to clean up some of the carbon deposits around the IAC and throttle body plate (take off the air intake plenum if its stock and open up the plate and see how black it is inside), warm up the engine, shut it down, slowly pour it thru the vacuum line while its running into the intake manifold, it'll clean the valves and around the injectors so everything sprays great... nasty white smoke will result, that means its working! (this stuff is a great as an injector cleaner aswell, and can be added to the crank case just before an oil change, worth its weight in gold i say, but it is abrasive, its NOT something you want to run all the time. just a good cleaning!)