11th Dec 2016, 02:43
A fluctuating RPM is the number one symptom of a bad intake manifold gasket. As the ECM tries to cycle off and on adding fuel to compensate for all the unmetered air, a loop effect happens... lean mixture... More fuel... Upstream O2 sensor sees it as rich... (Downstream O2 sensor sees it as rich, or not, and if not your precat is getting killed anyways)... And the fuel is then lessened to once again create the lean mixture, setting the next cycle of fluctuating RPM.
11th Mar 2013, 15:45
First of all, to set the TPS, adjust it so you hear a click just as the accelerator cable i.e. the gas pedal is pressed. The cam or lever the gas pedal cable connects to; as soon as the pedal causes the accelerator to move, you should hear the click. If this doesn't fix the issue, check the O2 sensor.