Q: gas gauge goes up and down while driving on flat roads

asked by on October 05, 2017

my infinti g35 is not getting the best of gas mileage or something is wrong with my fuel gauge it has been tested it has power it is just not accurate sometimes i notice when i fill up my tank it stops at 7/8 of tank on the gauge it wont go to full like normal cars would so when i driving on a flat road that is even my gas gauge will start to go down like i lost fuel then comes back up on its own to the same spot were it was not sure what to change or have looked at this point this issue is really getting frustrating not knowing how much gas is left before empty last time i was at the pump i filled up the pump stopped i started my car and it went to 7/8 full instead of all the way full like its suppose to i thought it needed more gas but no it started over flowing out my tank when i did that so that let me know then i was full but when i left it still stayed at 7/8 sometimes i come back out to start my car my gas gauge will register under 7/8 begin driving a few miles and its at 7/8

My car has 139000 miles.
My car has an automatic transmission.

The most common cause of erratic fuel level is caused by a defective fuel level sender in the fuel tank is defective or out of position or restricted from going all the way up to full position. I would recommend replacing the fuel sender in the fuel tank and at same time replace fuel pump and filter so you do not have to pay for additional labor in the future to replace pump or filter.

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