Q: My car won't go past 20mph. I've gotten the codes, battery, alternator check. But after jump starting battery everything is fine.

asked by on June 21, 2017

After a long day of driving throughout the city my car didn't want to start. So I tried starting it again and it did. But I couldn't go past 20mph. I let my car sit in a parking lot for at least 30 minutes then drove it home. It still wouldn't go past 20 mph. After making home. My brother mentioned maybe it's the battery so two hours later he came by and jumpstarted my battery. I drove it around the block afterwards and everything was fine. The next day I took it to O'reily auto parts to get the codes ran on it and everything was fine except for my emissions valve. My alternator was good and my battery was good as well but needed to be charged. Could my battery be the issue or maybe a sensor or something else?

My car has 120000 miles.
My car has an automatic transmission.

Hi there. The job of the battery is to provide electrical power to start the engine or power accessories when the vehicle is not running. When the vehicle is running, the alternator takes over the job of supplying power. Due to this fact, I doubt that the battery is the cause of the lack of acceleration problems you are having. I would suspect that this is caused either by a sensor that is faulty, or an ignition / fuel system component that is dirty, has a bad electrical connection or is damaged and requires replacement. It’s probably best to have a professional mechanic come to your location to complete a car is slow to accelerate inspection to determine the source of this problem.

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