Q: My system says there is water in the fuel

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Notice a little knocking when slowing down running rough and clears up if I punch it it don't knock will water cause knocking

My car has 300000 miles.
My car has an automatic transmission.

Hi. Yes, water in the fuel will cause knocking. I would advise doing a fuel system maintenance - drain the fuel system all the way to the tank, including the tank. This will get rid of any water and contaminated fuel.

I recommend replacing the fuel filters. If after servicing the fuel system, the knock is still there, most likely you have a sticking fuel injector and the injector will need to be replaced. If you would like to have this checked in person, a certified technician from YourMechanic can come to your location to diagnose the water in fuel and follow through with any needed repairs.

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