Jeep won't turn off

I have an 86 pioneer 2.8L that will "deisel" after I turn the ignition switch off. Just keeps trying to idle, although very rough and probably missing in a few cylinders. It runs and idles fine when ignition switch is turned on. I haven't done any diagnosing and before I tear into the switch itself I was hoping that someone might have some insight on other culprits such as improper vaccum hookup/ carb adjustment/ that kind of thing. I just don't want to miss anything or dig to deep if it may be something simple. thanks

could be a multiple of things....


idle speed to high
ignition timing not adjusted properly
intake leak
carbon build up in the cumbustion chambers
valves sticking
valve clearance isnt properly adjusted
EGR system faulty
Overheating causes
and last but not least
the fuel pump shut off solenoid might not be operating properly