engine problem - bad power,mpg, & sounds

Alright, here are my symptoms and thoughts.
#1 - bad mileage, went down 4 to 5mpg since problems.
#2 - bad power, any sort of an incline and its shifted down and reving at 3500.
#3 Idle stutters/blips up every second or 2
*#4-the wierd sound... ok, so i here it very prominently when the jeep shifts from 3rd to 4th and its around 43mph so its rpms are really low. At this point i hear a clack clack clack noise and it gets quiter as rpms go up, but never completely goes away
#5 on occasion when i turn off my car, the engine does die right away but clacks once or twice and then dies.

Ive done a full tune up and that didnt help much. I dont know if maybe my timing is off maybe stuck lifters or valves. All the shops ive taken it too are morons and say nothing is wrong so i'd like to go in there with some directions to lead them in.

Broken flex plate

I have a 1992 XJ with an auto trans. Had same symptoms & turned out to be a broken flex plate (fly wheel). It would be my recommendation to get a new one, do to this being a common problem. Also consider replacing the starter, it may have helped or caused the problem. Hope this helps!!!

#1 o2 sensor or catalytic converter or bad plug wires
#2 tps, vaccum leak, fuel filter????????
#3 vaccum leak, fuel filter?????
#4 without more info...I think chipmonks
#5 Clean intake mainifold and tb with Seafoam...that noise is caused by cabon igniting after the engine is tunred off

also keep in mind that the crank sensor is ran off the flex plate so it will effect timing & driveability also. Just remove inspection cover. They usually crack around the crank.

#4 check u joints. common culprit, easy diagnosis. grab and wiggle: note any play or slop