The Throttle Position Sensor can get out of adjustment due to wear in the throttle body or due to carbon build up. This will cause the idle timing to advance more than 30 degrees which will cause very high HC and NOx emissions. Conversely, the Throttle Position Sensors can wear out and not properly advance the timing which causes a lack of power and poor fuel economy.
Car Problem Reports
Toyota T100 Throttle Position Sensor Out of Adjustment Due to Wear/Carbon Build-up
Toyota T100 Problem
Average Mileage: 181,000 mi (160,000 mi - 193,000 mi)