Engine Shudder on 1997 Jeep Grand Cherokee

I have had this problem for some time now and can yet find a solution. My jeep has not shut off on me recently but ocassionally the rpm will drop while at a stop light and sounds like it might. It also will do it during a drive. I have noticed it only dose this when the engine temp reaches between 180 - 210 anything below 180 the engine runs fine now before I had the Cat and muffler changed it would shut off at that point. Now it just shudders like crazy. There are new Spark plugs, wires, cap, rotor, pick up coil, coolant senser, CAT, Muffler, fuel pump, and i also put some cleaner for the injectors and still the problem is there any suggestions plse. my next step is to change the IAT sensor or the Throttle Position Sensor.

Asked by for the 1997 Jeep Grand Cherokee
Were you able to get this problem resolved? I sure would like to know what it was!
I say this all the time about car repair, "man made problems are the hardest to diagnose".
Was there ever any diagnostic trouble codes stored in the pcm?
Thanks for posting the solution, hopefully someone will see this before getting too deep into trying to diagnose the problem.
Yeah I did come to find out a while back i installed the crank shaft sensor and removed the spacer by accident someone told me that i wasnt supposed to do that and recommended that i put a peice of card board in place of that spacer i removed so i did it fired right up and i thought nothing of it. that was 3 years ago now that i had the Cat Converter replaced it was causing problems. Why! well for one the timing on a jeep cannot be adjusted soooo this little magnetic device that was not install right caused my cylinders to misfire which cause the ingine to either fire early or late causing fuel to leak into the cat and ignight also make ther tranny feel like its sliping... Damn a 35 dollar part that cost me too much to figure out but now i have practilly a brand new car and I LOVE MY JEEP