Q: won't go over 40 mph

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Lets start off by saying this does not happen all the time but it is getting more frequent. We will drive the car straight for about an hour to an hour and a half. everything is fine and then all of a sudden the car will not go over 40 mph and struggles going up hill. I have had it to my mechanic 3 times for this problem. while they changed some things it has not changed the problem. Nothing they did worked. What could be wrong. I can't trust my car!

My car has 120000 miles.
My car has an automatic transmission.

A: This is a sign of a <a href='https://www.yo...

This is a sign of a faulty throttle position sensor. This is a sensor that monitors the position of your foot on the gas pedal and relays this info to the car's computer which then tells it how much fuel to introduce to the motor. When this is not working properly it will cause the car to go into limp mode occasionally, which is why the car wont go over 40mph. I would recommend having an expert from YourMechanic come to your home to diagnose your vehicle's acceleration issue and replace your throttle position sensor.

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