Q: I changed my TPS because of bad idle, now it stalls when I come to a stop after exceeding 50mph. What's the problem?

asked by on February 16, 2017

I changed my TPS, because before it was idling really bad to the point of shutting off before I even put it in drive. Yet now that I have changed it, it stalls when I come to stop and the acceleration is struggling. I also cleaned the idle air control valve because it was dirty. To reset the computer I disconnected the negative on my batter and the Throttle position sensor for thirty minutes. Before I reattached the negative I reattached the TPS, yet it still doesn't seem to want to match up and work right. What seems to be the problem?

Hello, It sounds like you may have a faulty MAP sensor that may be creating an adverse signal to the change in engine load. The Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the [MAP sensor]((https://www.yourmechanic.com/services/manifold-absolute-pressure-sensor-map-sensor-replacement), it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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