Best of Deals Car Reviews Repair Shops Cars A-Z Radio Show

02 buick le sabre flow sensor issue

my mom took my car to the repair shop for me because my engine light is on. I’m not sure what the code was that came up. She brought me back the car and said the shop said it’s a “air flow” thing that’s going to cost me $300 to fix. Has anyone had this issue or even know what this means. Can anyone tell me what they think it could be

The computer decides how much fuel is injected into the engine based on how much air is sucked into it. When that sensor goes bad, it gets no such info. It now estimates how much fuel the engine needs based on the throttle position and the estimate is usually on the high side just to ensure that there is enough fuel to burn. Prolong driving like this will cost you more than extra fuel. It’s possible to damage emission equipment

Informative post above. The engine requires a precise ratio of air mass to fuel mass to work correctly. The chemical reaction that happens inside the cylinder is (approximately) CH2 + O2 == CO2 + H2O. You could, if curious, get out your high school chemistry book and determine the weight of each of those atoms and figure out the correct mass ratio of air to fuel if you liked, provided you knew how much O2 is in air, about 20% as I recall. (You’d have to properly balance the above eqn first.)

To get the ratio correct, modern auto engines use a mass airflow sensor (MAF) to measure the air mass being sucked into the engine for a given driving situation, then the computer calculates how much fuel to inject to get the right ratio of air to fuel. That’s not the end of it though. Next the same computer double-checks whether this amount of gas is actually correct by measuring the amount of oxygen in the exhaust. If the air/fuel ratio is correct there’ll be some oxygen in the exhaust, but only a tiny amount.

What that code is saying is the double-check the computer is doing is showing something is not working correctly. There’s either too much O2 or not enough in the exhaust. There’s a few likely culprits to consider first

  • The MAF is faulty, maybe b/c it isn’t plugged in, it’s dirty, or the heating circuit isn’t working
  • The O2 sensor is faulty
  • The injectors aren’t injecting the amount of gas the computer thinks they are; e.g. clogged injectors.

There’s usually several different diagnostic codes which apply to the MAF function, so you’d need to tell us your car’s make/model/year and the actual codes read if you need more info. There’s a test available using the manufacture’s diagnostic equipment (like a dealership shop would have) that is able to measure how much extra or how much less fuel is actually needed to be injected to achieve the correct air/fuel ratio. That can be useful to help narrow the source of the problem down.

You can read more about how a mass airflow sensor works below.

$300 isn’t too much to replace the mass air flow sensor on that car. It could be much worse.