Skip the auto shop - Our mechanics make house calls

Q: Car engine brakes on its own.

asked by on

When I'm accelerating and the car changes into second gear it'll downshift hard on its own and it makes a little whining noise. I know it's not the tranny. Could it be the MAF or IAC ?
My car has an automatic transmission.

What you are describing is often a sign of low transmission fluid or a faulty transmission control solenoid. As you know, automatic transmissions use pressurized hydraulic fluid to change gears. Every time a gear change is required, the car’s computer activates a transmission solenoid, which directs transmission fluid into the valve body to engage the correct gear. When this is faulty or not working properly, this can cause a delay in gear shifting or in some cases cause the car to not shift at all. This type of problem is amplified any time the transmission is low on fluid creating a drop in hydraulic pressure. I would recommend having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

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: Why is my car still misfiring and smoked when idling

Engine misfires can be caused by many different problems and are generally caused by either a spark or fuel issue or in some cases, a combination of both. Spark related problems generally will result from things like ignition coils, crankshaft...

Q: Possible injector issue?

Hi, thanks for writing in. A knock in a diesel engine usually indicates an injector issue. Either an injector is not working or the injector pump is not pumping on that cylinder. I recommend having a diesel-savvy technician check each...

Q: When trying to reverse my clutch makes a grinding noise and stalls out. Also when driving down the highway theres a rattling sound

The rattling noise under the vehicle could be a loose heat shield that could be moving around when the wind is moving fast under the vehicle. For the grinding issue when going in reverse, the reverse gear could have broken...

Related articles

How Long Does a Heater Control Valve Last?
Keeping the right amount of coolant in a car is essential in keeping the engine at the right temperature. Failing to have the right amount of coolant or even bad elements...
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...
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...