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Q: How can I be sure i am having a Throttle Position Sensor issue?

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When I come to a stop and then pull out my ML320 does not respond to the throttle. Although it will begin to slowly move and pick up speed but it still does not respond to acceleration attempts. Finally, after numerous attempts, I shut the ignition off and more often than not the problem disappears and it resumes normally to giving it gas.

My car has 135000 miles.
My car has an automatic transmission.

Typically a throttle position sensor (TPS) is tested using a multimeter. The specs to compare against are published in the Factory Service Manual. As long as the TPS tests within the range of published values, and does not display intermittent or sticky operation, you can assume it is good. There are other components within the air induction system that should be considered such as any mass airflow sensor, idle air control valve and so forth. Faulty EGR systems, and fuel system deficiencies, can be a part contributor to the acceleration problem you are describing. In addition, the fault may not be component related but rather wiring or ground related. Of course, an attempt should be made to see if any Diagnostic Trouble Codes have been set in the PCM which codes might provide clues to the origin of the fault. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, please request a poor acceleration diagnostic and the responding mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic.

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