How to Adjust the TPS on a GM TBI The throttle body injector (TBI) of a vehicle helps control the throttle and maintain the minimum revolutions per minute,or rpm. General Motors vehicles use the TBI in the same manner as most automobiles. To adjust the throttle position sensor (TPS) of the TBI,you must remove the TBI and alter its makeup slightly. Turning the TPS down may help improve the way your vehicle runs,but if you turn it too low,your vehicle may not start. Adjusting the TBI requires precise movements and should only be attempted by someone familiar with GM engines. Things You'll Need Allen wrench Multimeter Screwdriver Instructions 1. Turn your car off by turning the key counterclockwise maxidiag elite md802 price. Remove the key from the ignition. 2. Open the hood of your car and locate the TBI. The location of the TBI will vary,depen ... Read more »