Skip the auto shop - Our mechanics make house calls

Q: won't go over 40 mph

asked by on

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.

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.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My car is making a new power steering pump noise

It may be possible that the smaller belt is putting too much additional stress on the pump itself forcing it to work harder than it needs to. This can cause this kind of whining sound just as a pump does...

Q: Car sounds rough...replaced clutch with no luck. Magically fixed today, but airbag sensor is on

You may have a clutch release bearing that is going bad. I have seen the bearing be noisy one day and gone the next. The clutch and release bearing should be replaced as long as the transmission is being removed....

Q: Hood will not open

The most likely route to open the hood is from underneath. You may have to jack up the front of the vehicle (follow proper jacking instructions). Once elevated, the belly pan may have to be removed to gain access. A...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...