Does The Knock Sensor Have Much To Do With Emissions And Gas Mileage If So, How Much

Posted in Crank, Oil and Piston
  • Give percents per gallon for gas mileage and overall effect on emissions. Thanks.

    There are 6 Answers for "Does The Knock Sensor Have Much To Do With Emissions And Gas Mileage If So, How Much"

    1. Heinz M says:

      There is no knock sensor. ~
      An engine knocks when being fed too low an octane rating fuel.

    2. I might be right says:

      Umm yes there is a knock sensor, it changes voltage from ac to dc or maybe dc to ac. It detects knock in an engine or pinging as it is sometimes called, and advances or retards the engine timing accordingly to make the knock go away. In that manner it could affect the gas milage if it is retading or advancing the timing incorectly. How much I dont know.

    3. autotechgenes says:

      a rattling sound is produced when detonation is caused by something other than your spark plug,such as a cherry red hot exhaust valve will explode the fuel before the plug,and if the piston is on its way up,it will come into an explosion,when done occasionally,its no big deal,but allot can cause a piston to melt.Knock sensor looks for this problem, the computer gets the input from the knock,and the computer retards the timing as best it can to eliminate the problem. In short the better running car burns less fuel. ( The octane in fuel makes gas more stable, it allows the plug to ignite fuel and not something else.

    4. Philip K says:

      Heinz is wrong, most fuel injection systems do have a knock sensor. This sensor does exactly what the name says, it senses knock. The moment that an engine starts to knock it will send a signal to the electronic control system and that will adjust the timing to minimise the knocking of the engine. It will have an efect on economy, if for instance it sends the wrong signal and the ecu retards the timing too much the engine will loose power and the driver will try to compensate by giving more accelator etc.

      Because the sensor works more or less like a microphone loose parts that resonate can cause it to pick this noise up as knocking. The ecu will then react to it while it is unnecessary to do adjustments. Economy and emission can suffer but how much will differ from case to case.

    5. motherof2boys says:

      If your vehicle is equiped with a knock sensor its effect on emissions is rather indirect.

      The knock sensor detects just that- Engine Knock.
      The pcm reading this signal will retard the timing if it detects enough knock. Now if your sensor is giving a false signal it can hurt performance and your mpg however not on a level that you would become aware of it. If you wanted to have it lookes at you would have to find a shop that has a computer capable of catching live data and not just pulling up codes.

      If you want suggestions on improving your mpg, ask in another question but include year,make,model,miles and engine.

    6. arseking says:

      buy a new car…too many problems with your nissan… oh; low bank account…

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