Have an 89 4L auto. 4 wheel drive. 159000 miles. Heres the problem. The jeep starts and runs normally. When I turn the key to the off position it keeps running, smooth idle, not dieseling, gauges all working. I pulled ign wire from fuse block and it still runs. Heres what I have tried, r/r ignition switch on bottom of steering column. Adj. is good due to the fact when the motor is cold, you can turn it off and on and it will shut off and start all day long. The problem seems to happen when the motor is hot. Battery is good, alternator is brand new, new starter. starter relay also tested good. If battery cables are kept on it, it will be dead in a matter of hours with the key in off position. I have never had a problem like this EVER so I am at a total loss as to what the problem could be. Have not noticed smoke or burnt wiring. I hope someone has had a similar experience that can help before I have a bonfire in my driveway!