WHILE TRAVELLING IN MORNING RUSH STOP AND GO TRAFFIC, IN AUSTIN, TEXAS I HAD TO COME TO A COMPLETE STOP. THE TRUCK WOULD NOT STOP UNTIL I APPLIED CONSIDERABLE BRAKE PRESSURE. I CAME WITHIN 6 INCHES OF THE VEHICLE IN FRONT. I WAS TRAVELLING AT APPROXIMATELY 1 TO 2 MPH AT THE TIME. ON THE RETURN TRIP IN THE EVENING RUSH HOUR IT WAS ALSO STOP AND GO. I HAD TO COME TO A COMPLETE STOP BUT THE TRUCK WOULD NOT STOP. I HAD TO PUT AS MUCH BRAKE PRESSURE AS I COULD TO SLOW THE TRUCK (DOING 1 MPH OR LESS). I STILL TAPPED THE VEHICLE IN FRONT. AT THE TIME I WAS TRYING TO STOP THE TRUCK, I HEARD THE ENGINE RPM REV UP AND A POPPING NOISE FROM THE ENGINE. TAKING THE TRUCK TO THE DEALER FOR A CHECK UP ON THE ISSUE.