AS SLOWING DOWN TOWARDS A RED LIGHT AT APPROXIMATELY 5 MPH THE ENGINE SUDDENLY REVVED UP . PRESSED BRAKE TO FULL (AGAIN, NO FOOT ON GAS), ENGINE CONTINUED REVVING AT HIGH RPM. JEEP LURCHED FORWARD THREE TIMES AND REAR ENDED CAR IN FRONT WAITING AT THE LIGHT. 4 WHEEL DRIVE WAS NOT MANUALLY TURNED ON, BUT FELT LIKE THE FRONT WHEELS HAD LOCKED BUT THE BACK WHEELS KEPT LURCHING THE JEEP FORWARD. AGAIN THE ENGINE WAS RACING EVEN THOUGH GAS PEDAL WAS NOT PRESSED. PLEASE NOTE: THIS VEHICLE IS A RENTAL FROM AVIS.