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Q: My car's fuel efficiency is poor and it starts rough

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I got my car read at autozone and they told me it's either the gas cap that went bad which I replaced still doing the same thing, purged solenoid canister, but I think it's the MAF also I noticed that my dipstick tube is non existing it's just the stick and oil is leaking but has no signs in the driveway

My car has 146000 miles.
My car has a manual transmission.

A: There is a valve that is by the fuel neck n...

There is a valve that is by the fuel neck next to the fuel filler inlet that measures the fumes from the gas cap and related areas. This valve is known as the EVAP purge solenoid valve. This valve controls the pressure in the fuel system.

If the valve fails, it will leak and the fuel vapor sensor will pick this up. When the valve fails, the computer will increase the amount of fuel to max and cause the engine to run rich and have a rough idle.

Check the valve with a fumes sniffer and see if there are any vapors present. If so, then the valve needs to be replaced. If there are no fumes present, then the valve still could have failed electronically.

If you need further assistance with your vehicle, then seek out a professional, such as one from YourMechanic, to help properly diagnose your car's rough idle and help you fix it accordingly.

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