My 1999 4.2 liter 6cyl Jeep Grand Cherokee occasionally will stall out while driving or at a stop for no apparent reason. It will either start up again or after waiting for a time period it will start just fine. There is no dash light, i.e.;check engine, battery that comes on, the car runs smoothly otherwise and the rest of the electrical will not be affected? I've found from my mechanic that this has occurred with other jeeps of the same specs. and could not be accounted for after spending money to replace things such as starter, distributer etc. through the dealer. The dealer said to check and monitor situation as "bad gas" or water in the tank and stick with Chevron. I've been a faithful user of the premium stations such as Chevron and Texico and have used other only in an urgency. Those are the symptoms...my question is do you know what this is?