94 grand cherokee 4.0l 90,000 miles. I just replaced the crank sensor because it wouldn't start. once i got it started it ran fine for 5 minutes and then started misfiring. I just put in a new cap, rotor, wires, and plugs less then 3k ago. It will run fine now when it's first started up until it reaches normal temp then it will misfire really bad like it's running on four cylinders or less and it will get worse the longer it runs. If it is shut aff for an hour after that it will start right up and run perfectly and the process repeats. could this be a computer issue? I get no check engine light when this happens either. will i still get codes when i hook up the scanner?