So it sounds to me quite like an electronic control problem.  It seems like there are several cases where the engine control logic prevents the throttle from being closed--for example, during startup there is a faster idle.  Similarly, during shift of an automatic transmission, there is some throttle control going on.<p>Thus, it doesn't seem too far-fetched to imagine that there is a glitch in the engine control logic that is pulling the throttle and hence the gas pedal in a way that makes it seem like there is a problem with the pedal itself.