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TPS Adjustment


Turn the key to "Run" but, do NOT start the engine.  Loosen the two bolts that hold the TPS in place enough that the TPS can be moved.  Note that the TPS is slotted so that the sensor may be rotated as well as moved fore and aft.  (The top slot affects the idle setting and the the lower slot affects the wide open throttle voltage)   Push the entire sensor as far forward as possible so that the two bolts are up against the back ends of the slots.  Then, rotate the top of the sensor CCW a bit until your scan tool indicates an idle TPS voltage of say 0.38-0.44 volts and tighten the retaining bolts so that the sensor cannot move.  Note that the idle may change as you move the sensor.  Don't be deceived that you have changed or improved the idle.  When you shut the engine off and restart, the idle will go back to where it was before you moved the sensor unless the sensor was out of range to begin with.  As stated prior, the ecm re-zeros the idle at each start.

The ecm does not look at tps voltage when adjusting fueling.  Rather, it looks at the tps percentage of full scale.  Whatever the idle voltage, it is auto-zero'd to 0 percent when the car is started.  Therefore fueling is not changed whether the idle voltage is 0.38 or 0.46 as the computer is feeding zero percent and commanding the fueling specified for idle fueling.  Once the engine is started, and the tps set to zero percent, any movement of the tps is reflected as percent change even if the change is within the idle window checked when the engine was first started.

Having set the idle voltage, now recheck the wide open throttle voltage.    It will probably be around 4.5 v. 

Go to the Throttle Position Sensor section of the Basics page and read the section in order to avoid falling prey to some of the myths surrounding TPS adjustment.