Q: Car engine brakes on its own.

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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.

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