Three problems related to speed control linkage have been reported for the 1999 GMC Sierra. The most recently reported issues are listed below.
While traveling on highway vehicle will acellerate suddenly. Dealership is aware of problem.
While pulling inside of the driveway and coasting along, engine just roared up and vehicle accelerated. Vehicle jumped over landscape timbers and hit basement wall. Also, front brakes locked up, but back wheels were still moving and in motion.
Throttle plate sticks at idle requiring additional force to release. This caused vehicle to fail to come out of idle at red lights and intersections. Dealership charged me repeatedly for cleanings and argued with me regarding TSB's about the throttle. I was told I was not supposed to have that information and it didn't matter. I was told throttle body systems are normal maintenance and the throttle body needed replacement every 10,000 miles. The drivers seat (manual) would unexpectedly release throwing me into the steering wheel. Plastic part broke from seat track. Dealership failed to fix, damaged the seat further trying to grind on the track and hammered seat track in the closed position to force the seat from moving. Charged me for damaging the seat. Gm customer service called to argue my complaints, I was told they didn't have any control over the dealership, and if they said the seat was fixed they would back the dealership. This is going to cause me to have an accident.