Runs good but idles bad

I have a 1999 Jeep Cherokee and it runs good while accelerating but at idle it runs like crap, like its bogging out and sounds like it wants to die. Some times it will even kill out but it starts up like a dream. Ive replaced the crankshaft position sensor, new distributor, new/used engine harness and pcm, new plugs and wires, tried different used sensor that i have laying around like tps sensor and idle air control valve also cleaned the IACV and the chamber it attaches to. Still runs like crap at idle and anything below 1250rpm when i drive it runs perfect. My check engine light comes on occasionally and i throw a scanner on it and it keeps throwing a bunch of random codes. Different each time.. Im at a loss and tempted to get rid of the thing. Help please.

 

Might look for a vacuum leak. Use a spray bottle with water on a cold engine. Spray on select areas (intake manifold, vacuum lines etc) one at a time listening for engine speed changes.

 

do you have a scanner or a code reader?
With a scanner look record and post - ECT, TPS, Fuel trims long and short, precat o2 sensor voltages.

Post the codes - might make sense to us.

Also jeep is STOCK powertrain wise anyway?

 

Also sounds like you may have a fuel filter that is clogged and at idle it doesn't have enough pressure to run well but under throttle it's forcing enough fuel to make it run decent.
Unfortunately the filter on the 97+ is in the tank as part of the fuel pump.
I would follow Awrench's suggestions first before dropping the tank to do a fuel pump.

Does your temp gauge work? I had the temp sensor come disconnected on my '00 XJ. The computer saw this as the engine being cold so it started dumping extra fuel to try and warm the engine up. This caused it to run rich and while it ran find under throttle it ran like crap at idle.

Just a couple of options.