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Q: Jerking/studdering problem

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My 04 Hyundai Santa Fe is acting up. I've sent it to the mechanics thinking I had a misfire but they say it isn't that or the spark plugs it's just the fuel system needed cleaning. So we allowed them to "clean" the fuel system. It stopped for a couple of weeks. At first when I would put the SUV in gear it would have a jerking motion. But it wouldn't happen all of the time. And after a few minutes it would stop and run fine. It did that for a few days then it stopped. And it's been several weeks since the "cleaning" and now it's acting up even at idle. It will have a hard "jerk" once then it will idle fine. It hesitates sometimes when driving and even now it will jerk once or twice while driving. And I am only going maybe 45-50mph. And sometimes when pressing the gas it will do this soft jerking thing. I am assuming it is the fuel pump and or filter. But it is inaccessible for my vehicle unless they drop the tank. Any ideas before I pay the money to have this replaced?

My car has 140000 miles.
My car has an automatic transmission.

A: Hi, thanks for writing in. This is a common...

Hi, thanks for writing in. This is a common sign of a failing mass air flow sensor. This is a unit that regulates the air flow into the engine as it is mixed with fuel prior to being injected into the engine. When this is not working properly or is dirty, this can cause an imbalanced load of air and fuel to be supplied to the motor. When this happens, this will cause the jerking feeling that you describe as the motor is starving for fuel. If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make or suggest any repairs as needed.

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