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Q: Drive-by-wire throttle problem

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My car has a Drive-by-wire throttle problem. When I am coming to a stop at a stop light or stop sign the engine is doing about 2600 to 4000 rpms. When I depress the clutch the rmps don’t drop. When I shift to neutral the rpms stay at 2600 to 4000 rpms until I press on the accelerator with my foot. Then it drops back to idle. This is an occasional problem that happens. I never know when it’s going to occur. The problem is worse when the engine is at operating temperature. I brought my car to the dealership, and they updated the throttle mapping software. But that is all they have come up with so far. Do you think it could be a sensor in the car? What other ideas do you have?

Hello. The symptoms you describe may be caused by issues with the throttle body or with the idle air control valve. The drive by wire system controls an electric throttle body which feeds the engine air. If the throttle body has any issues, it can behave erratically and cause the high idle symptoms you are experiencing. A possible sensor that could also be producing these symptoms is the accelerator pedal position sensor. As its name implies, the accelerator pedal position sensor detects the position of the gas pedal, so that the throttle body can be opened accordingly. If the sensor has any issues, it can also cause the throttle body, and therefore engine idle speed, to behave erratically. As electronic engine performance symptoms can be difficult to pinpoint, a proper diagnosis is highly recommended.

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