just got a 88 XJ with a 4.0 through an auction. it is stuck on a high idle about 2500 my tach is not accurate. I checked for vacum leaks and also replaced the MAP senor and Idle Speed Stepper Motor, the idle speed motor is not closing. The other problem that I have, after running for 15-20 min the truck just dies, I changed out the coil with a new one and then I also changed out the coil and ignition control module with a used one and both times I got the same results.