Q: Bad gas mileage, engine misfire - 1992 Cadillac Allante

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My car has a mileage of 132,000 miles. I've been getting a really bad gas mileage. It's 11 mpg on average. The engine has been misfiring a lot as well. I had the car tuned up recently but there was no improvement in either whatsoever. What should I do?

There can be multiple causes, but it sounds like your fuel injection is injecting too much fuel into the engine for the amount of air it’s using. Faulty temperature, air flow, or oxygen sensors, a dirty throttle body or incorrect fuel pressure are some of the more likely candidates. A professional mechanic, like YourMechanic, can diagnose this for you and make needed repairs to all of these issues, including cleaning the throttle body and replacing the oxygen sensors.

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