I have a 99 xj with 281,000 miles on it, I'm trying to correct the rough idle and when coming to a stop then pressing on the gas to go again sometimes it almost dies. Also the start is horrible, I have to really crank it to get it to start. Most times it will stat but it has really low RPMS for a couple of seconds and then it shoots up to about the 1 mark. I tried priming it by turning the key several times but that doesn't seem to help. The check engine light is on and it has the PO304 code and PO172. Which I think means misfire in cylinder 4 and that its running rich. I just switched the spark plug from cylinder 4 to cylinder 3 today. I'll keep an eye on the code to see if it switches. Also while looking at the spark plugs it looked like the one on #4 had a smaller gap so I raised it a little.

Work done:
Injectors
cap rotor and spark plug wires
spark plugs
seafoam
Ignition Coil

Any suggestions would be great thank you!!

 

Does the fuel pump prime everytime? Check the fuel pressure and look for any vacuum leaks. Check the battery voltage. Clean the IAC and throttle body. Could even be a failing TPS, injector, or a cat thats starting to go. Diagnose what you can.