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Q: Hesitation at RPMs lower than 2000

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My vehicle has hesitation problems at RPMs lower than 2000. While driving and accelerating up to 2000 RPM, this problem occurs. It seems like it doesn't get enough fuel or air. This is not such a big deal when the engine is cold. The car drives well at RPMs higher than 1700. I had a fuel filter and air filter replaced. Also, the MAF sensor and fuel injectors were cleaned. There are no error codes appearing. Several mechanics ran diagnostics and cannot find the reason for this and the hesitation issue persists. Can you give me some advice? Thank you.

A: The vehicle may have unmetered air entering...

The vehicle may have unmetered air entering the engine, which is air entering the tubes between the mass airflow sensor and the throttle body. If there are no leaks, then the fuel trims in the data would need to be inspected, to determine if the two front O2 sensors would need to be replaced with the new part number. The O2 sensors give fuel control feed back to the ECM and if the system is too lean you will get a part throttle hesitation. The technical bulletin is 03-09-11 and the new part number to replace the O2 sensors is 3S4Z-9F472-BA. This part may have been updated since the bulletin. If you need to get your O2 sensors replaced, consider a certified mechanic, such as one from YourMechanic to come to your home or office to replace your O2 sensors.

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