2008 PONTIAC VIBE Power Train Problems

FEB 3, 2011 WAS THE FIRST OCCURRENCE. I PUT THE CAR IN REVERSE THEN PULLED FORWARD, TURNING THE WHEEL TO THE RIGHT TO GIVE MYSELF ROOM TO BACK UP AND TURN MY CAR SO I COULD PULL OUT ONTO A BUSY STREET GOING FORWARD RATHER THAN BACKING OUT INTO TRAFFIC. I WAS GOING VERY SLOWLY AND APPLIED THE BRAKES WHEN THE CAR SUDDENLY ACCELERATED VERY FAST. IT RAN UP AN 18" ROCK WALL, PUSHING THE BRAKE DID NOTHING, I TURNED THE WHEEL TO THE RIGHT TO AVOID A TREE WHILE STILL TRYING TO BRAKE. THE BRAKE FINALLY HELD. A TIRE WAS DESTROYED, IT WAS REPLACED AND TAKEN TO MY MECHANIC WHO FOUND NO FURTHER DAMAGE AND NO REASON FOR THE ACCELERATION. AFTER LEAVING THE MECHANIC I NOTICED THAT IT SEEMED A BIT JERKY. TWO DAYS LATER I TURNED THE CAR ON WHILE SITTING IN A PARKING LOT WITH MY FOOT...