Q: I'm wondering why is my car slow to accelerate and gets up to about 40mph before the mph hand falls down.

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I could be coming to a stop and if I'm on a hill it would be harder for me to accelerate . I could be going a certain speed then it would lose the energy to go seems like it . The Rpms still rises but it won't go . I would have to cut the car off ,crank it back up , put it in drive and it might go on the first try but if it don't I cut it off again until it decides to go when I put it in drive and once I start driving not even 5 minutes the mph hand falls down . Somebody said it could be the fuel pump and another said it could be transmission slipping I'm wondering what y'all think.

My car has 250000 miles.
My car has an automatic transmission.

Hi there:

Traditionally, vacuum leaks or obstructions in fuel flow tend to cause acceleration issues. This could be triggered by a bad mass air flow sensor, EGR valve or clogged or dirty throttle body that simply needs to be cleaned to remove carbon deposits. The best way to determine the exact source of this issue is to contact a local mobile mechanic to complete a car is slow to accelerate inspection.

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