Skip the auto shop - Our mechanics make house calls

Q: SUV slowed from 60 to 40 mph and lost acceleration

asked by on

While driving over 60 mph on a busy highway, my SUV suddenly slowed to 40 mph and It thought it was going to stop. I pressed the gas pedal, but it did nothing. Then I tried to move to the right to avoid having an accident and while doing this, the SUV independently shifted and started accelerating again. After that I got off the highway and took back roads to get home. The next day I took the vehicle to the dealership and they could not find anything wrong with it. The engine light had been on for over a month, but even with that, they couldn’t locate the problem. They told me to come back if it happened again. One night I went to the store and on my way back to the house, the SUV completely stopped in the middle of the street, fortunately near the house. A neighbor helped me push it into the driveway. The next day it started and I took it to a different mechanic to have it looked at and the new mechanic told me the same thing: he would have to experience the problem before knowing what to do. I feel totally unsafe in this SUV. I don’t understand why the diagnostic tests don’t show anything. Can you give me any advise as to how to find the problem for this?

A: Diagnostic codes can be somewhat transient....

Diagnostic codes can be somewhat transient. If the engine management system observes the problem clearing after several drive cycles, it will turn off the Check Engine Light and clear the problem code. There is no "history file" kept. There are devices available to the dealer which they can temporarily install which can capture the state of the system when the driver presses a button for instance, allowing capture of temporary problems such as this. You can also purchase a device which plugs into the diagnostic port of your vehicle (On-Board Diagnostic II), which comes with an app which runs on your smartphone. This allows you to access the diagnostic codes immediately when the Check Engine light comes on, so that you can have a better idea of the problem.

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: Car keeps dying even though I jump it and the battery is less than a year old

Hello. This is not caused by the battery most likely. The alternator may not be charging the battery and, after you jump start the battery, if the alternator is not recharging it, then the battery may be able to only...

Q: The throttle keeps sticking at average speeds

You may have a damaged throttle body or a faulty throttle position sensor. Both of these issues can make you feel the same symptoms as a sticking throttle. I would recommend having the throttle body and throttle position sensor inspected...

Q: Transmission making noise

A transmission has many parts both mechanical and electronic. If your transmission is making noises, it is going to need internal work done to it. A rebuild will fix the issue with the transmission. As for the ABS Light being...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...