2004 Chevrolet Impala gas cap keeps coming loose

by Cher
(Toronto Canada)

My gas cap has become loose a few times over the last couple of months. Prior to discovering the loose gas cap, my engine light comes on which prompts me to check the gas cap. The engine light came on today, so naturally I did a gas cap check. It was so loose, it was barely sitting there. I tightened it, but the engine light is still on. I understand it may take a few trips for the engine light to go out if indeed the loose gas cap is the cause.
I don't understand why my gas cap is coming loose so often.

Steve Says,

The most likely cause of your problem is a defective gas cap. You will most likely just need a new one. It is possible that the piece that the fuel cap screws onto is bad but not likely. You can check to see if the threads are still good and if they are then it is probably a gas cap problem.

The check engine light should go out on its own eventually. I recommend that you just take it to an auto parts store and have them read the codes. Most of them will do this for free and then you will be more sure of what is causing it.

When they read the codes there will probably be an EVAP code. It is a code for the Evaporative Emissions System on your car and that is what the gas cap is part of. They can also reset it so the check engine light will go out.

Good luck with your car problem and I hope this has helped.