I'm having an issue with my 1999 GC Laredo 4x4, automatic tranny and I6 motor, and I'm hoping someone can help. When I first start it up and drive it, it runs like a top. After a while, it will start to die at red lights. No sputtering, no abnormal vibrations. It's like someone just turned the key off. And then it starts back up like nothing happened. It also "hiccups" when I'm driving on the interstate. It feels like when you pop the clutch on a manual to get the motor going, but it does it at 60 mph! I have replaced the computer, the ignition switch and wiring harness, and cleaned the IAC sensor. Any ideas on what else it could be? I'm praying that someone will be able to point me in the right direction...

 

Try the crank position sensor?