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Q: Car is shutting off while driving

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My car is occasionally shutting off and having trouble when starting up. The battery/electronic components are in perfect working order. Therefore my main suspicion is that it has something to do with the way that gasoline is delivered into the system for the following reasons: 1. The gas cap reads "turn until you hear a single click", however the cap no longer clicks at all when turned all the way. When turning the car on after filling it up I have to step on the gas pedal for roughly 30 seconds in park before proceeding in drive otherwise it will shut down. 2. When the car was new, the check engine light turned on a few times and the dealer said it was something to do with the gas cap not sealing properly. At one point they replaced a meter inside the gas tank. 3. When the car shuts off when running, it is only when I'm in stop and go traffic. When I'm driving at normal speeds, it runs normally. My question is this: Would replacing the gas cap make a difference, or is it the fuel pump or some other problem?

The first thing to do is to have the fuel cap replaced. The cap may be overtightened, causing gas tank venting to be blocked. If this gets blocked then the fuel tank can go into a vacuum and cause the stalling. If pressure builds up in the tank it could not release excessive pressure if the cap’s vent purge system is not working properly. Have the check engine light scanned to see the codes in the system and replace the fuel cap. Make sure you are using quality fuel and no E85 since it may cause problems in the fuel system of your car. This fuel is mostly alcohol and will cause reduced performance in vehicles not equipped to use it. You may need to have the throttle body, idle control valve, and mass airflow sensor cleaned. Make sure you are not using an oil type air filter as this will damage the mass air sensor. If you need assistance with this, a certified mobile mechanic from YourMechanic can examine your vehicle at your home or office.

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