general problems of the 2006 Buick Lucerne

I been paying alot to fix this vehicle every thing keeps going wrong with it and I don't feel safe.

Vehicle is a 2006 Buick Lucerne cx with 40,000 miles. About 2 months ago it started to go dead without any warning. The first occurrence was Jan 15, 2014 with my wife driving. The next shutdown on Mar 4, 2014, occurred in rush hour traffic. There was an audible signal accompanied by a “service traction control” warning, followed immediately by a throttle control warning and complete engine shutdown. I was able to coast across 2 traffic lanes into a parking area with great difficulty while steering and braking without power assist. Tried to restart the engine but got “throttle disabled” message. After 2-4 minutes was able to restart with no warning light illuminated. The last shutdown was on March 10, 2014, on the interstate at 70 mph. I had disabled traction control earlier in hopes of avoiding another unexpected shutdown. After coasting off the interstate, I was able to restart normally after a few minutes. No warning lights appeared after the restart. Two gm dealers checked the car on Mar 11, 2014. The first was a Chevrolet dealer, and after some diagnostic work they sent me to a Buick dealer down the street. Both dealers said there were no error messages and they could not repair. They said when it happens again to bring it back in immediately for diagnosis. The 3 shutdowns have been on cold mornings, temps less than 40 degrees. I believe in all three cases the warning “watch for icy conditions” has appeared prior to failure. This is an extremely dangerous failure mode that leaves no tracks if there is an accident! my wife now refuses to drive the car, and I am very apprehensive about it.

This has happened at least 4 times. We asked the Buick dealer if there have been any complaints and they said no. It has happened the last 4 years and again today and it is kind of scary as it could be dangerous if we didn't put our foot on the brake firmly when it happens. What happens is if we are pulling into a parking place or our garage slowing to a stop the accelerator goes down on its own and if we did not put our foot on the brake it would take off on its own. It last only a few seconds maybe 5 or so and then it stops. We have checked the floor mat and this is not the problem.