Slowly, over time the accelerator pedal began to stick when it was closed for a few moments, like at a stop sign. Then you would have to push it hard enough to get it to move that the car would almost squeal the tires once it came loose. The fix was to remove the air intake tube from the throttle body and spray throttle body cleaner on the inside of the throttle body around the throttle butterfly. Brush-wipe-spray-wipe until it is clean. Problem solved, and it has stayed solved for 15,000 miles so far.