A number of postings here indicate better mpg when using higher octane gas, because the ECU retards the ignition when it detects knock with lower octane gas.

A little logic is a dangerous thing...
In interest of fuel economy, if I remove the knock sensor, timing should be advanced, giving better economy. If I unplug it, ecu would probably detect it is missing. So I just unbolted it from the engine and tie-wrapped it to the harness nearby. Ran a couple of days no problems, engine seems like normal. Today on the on-ramp, got above 3000 rpm and the check engine light comes on. code 1-4-3, faulty knock sensor signal. reset the code, try it again. at 3000 rpm code comes back. (I don't usually get to 3000 rpm in my driving). Swapped it for another and got exactly the same results.

So the sensor is listening for engine noise only above 3000 rpm?
Does it work below 3000 rpm?

This is first car where knock sensor is not my own ears.

Arthur
89 245 430K km