My 2003 Jeep Grand Cherokee began hesitating\bucking at high speeds on a long drive yesterday. It is a 4.0 L. The truck drove fine for about 150 miles and then it bucked two times, as if I had let off and reapplied the gas too quickly. On the return trip, the truck bucked violently every few minutes when accelerating but never completely stalled. It happened above 1500 rpms and over 50 mph. Last year I put in a new TPS. This week I cleaned out the throttle body with method 1 from wjjeeps.com and added a bottle of Lucas upper cylinder lubricant with a tank of gas before we left. There are no check engine lights or codes. I am going to try to clean the throttle body with method 2 today. Any other thoughts? Appreciate the help. April.