MX5Ireland

Hi, my knock sensor seems to have stopped working, I suspect the sensor is dead but wondering if anyone knows if there is a way to check continuity between the sensor head and the connector blades?
I've verified that the RCA cable and the wiring down as far as the ECU is fine.
Its a Bosch sensor, part# 0 261 231 006 and looks like this :


The engine is fine for the moment without it, I've upped master fuel so its running quite rich (bangs, pops, burbles, the odd flame) just in case.

found this, off out to test

its a microphone so it's a coil, it should have resistance with the ohm meter. Alternatively, you can connect the 2 pins to a minijack cable, then to a stereo or amp, and see if it works..
Nico

yep, tried plugging it into my phone with music playing, no noise on the keypad, not sure if I need something louder.
Have tried checking resistance between pin 2 and ground but am not convinced I'm doing it correctly. Will drop into auto electricians tomorrow.

sorry I didn't mean to use the sensor as a speaker Steve. Although it could probably work, it might also damage the sensor.
i meant to use the sensor as a microphone. In my 205 I have a knock sensor hooked up to a Maplin mono amplifier and I detect knocks with headphones, like an electronic stethoscope.
I wired one for a local garage the other day, and if you tap the sensor out of the car with your nail you can clearly hear it in the headphones..

yeah, thats kinda what I meant too, I connected it to the wires on the output side of the sensor when verifying the wiring was ok.
I haven't tried using it as a microphone yet... I'll give that a go later.

Is knock v.clear when using headphones? Does it rise that high above the background noise of the engine ?

It's hard to describe. You can hear the valvetrain all the time, and the frequency and volume rises with RPM so it becomes very noisy, but knocking follows a more "analog" pattern that you can hear quite well, that doesn't occur regularly like other noises.
I trained my ear by using sample audio files that I found on a website, i think it may have been the manufacturer of the Phormula K4 who had a bunch of samples in their download section. I'll check if I can find them and edit this message

EDIT: can't find them, sorry.
You might check this instead:


Ideally you want to train on a N/A car as it's harder to break stuff than on your turbocharged MX5! When I started mapping the 205 it was N/A and I had a quite agressive timing map and knocking would occur only in low RPM / high load ie fifth gear at 1k rpm wide open throttle. And I couldn't hear anything when running Ethanol e85. removing 5º would make the noise disappear. You might want to induce knock somewhere safe to train your ear to it..

Nico