I'm trying to understand the advantages of lambda and MAF while I drive an old car, those parts are worn.

How come I have loss in fuel efficiency while there is no gain in performance?

  • Getting more (power, torque) for less (fuel) is what efficiency is. MAF and O2 along with other sensors help the ECU establish the most efficient work mode for an engine. When these are not functional, the efficiency drops and you burn more fuel for less performance gain.
    – max
    Nov 22, 2019 at 6:35

1 Answer 1


The engine ECU uses the readings from these sensors to get the fuel to burn as weak as possible while still being efficient and keeping the burn temperatures safe for the engine.

If the MAF and O2 sensors are not giving valid signals, the ECU will have to err on the side of caution and make the fuel mixture rich to ensure that the engine cannot be damaged by excessive burn temperatures. This will cause the engine to use more fuel and since it is now not burning the fuel at maximum efficiency, then you may even feel a drop in power output.

Burning more fuel does not always equate to more power, you need to add the correct amount of oxygen to make good use of the fuel. Adding too much oxygen can also cause excessive heat and a more explosive mixture which is not good for the engine.

  • Thank you for your insightful reply. Is it true that worn o2 and MAF make a car put out environment unfriendly fumes? I know I started with a o2 and MAF question but in the end I would like to learn what a Euro norm 1 catalyzer catalyzes and what not. Nov 24, 2019 at 20:46
  • @RichardCedric probably best that you ask another question so that it is visible to more people.
    – HandyHowie
    Nov 24, 2019 at 20:56
  • Yes I understand Handy but I insist on replying to people that give thoughtfull answers and also change a cold topic to a good read for the people that like reading or hope to find more answers. Will start another topic. Nov 25, 2019 at 19:28

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