What can cause knock values to appear?

[andysmee]

Another cheap and cheerful way of testing the sensor is to buy a bottle of octane booster and apply it to half a tank of fuel. You should see a resulting reduction in knocking - if so, the sensor is probably working...

[nikp]

I need to clarify the \'additional grounding\' comment i made: What i meant was, on the electrical diagram, Mazda seem to have additional grounding along with the ground to the engine. It\'s all standard stuff.

Which is why it brought me onto that question - could it be a grounding issue - but even if it is, i have no other issues anywhere else! But i was missing the ground wire that goes from the upper inlet manifold to the body connection - i have put that back on now.

[nikp]

Here\'s a cut out of the section with the knock sensor

[nikp]

Had a check around last night - probably didn\'t help that the trailing plug on the rear rotor didn\'t have a firm enough contact with the HT lead, and even worse was actually loose in the hole. I corrected both issue...and for a good amount of time though i had sussed it - didn\'t get any higher than 24 knock, even under boost. Then it hit 68! :reallymad

So, back to the drawing board. I\'m starting to wonder whether it might be the secondary injectors. They\'re second hand 1200s, and the wiring to the front one is a bit iffy. I know, i know - sort the wiring and get better injectors! But they cost soooooo much! :p

[nikp]

Ok, i have an update for anyone who may, or may not be interested.

Firstly, i have found out that the knock sensor wiring is shielded - presumably to minimise interference from other electrical devices. Now, i have located the wiring for the knock sensor, and it\'s in bad shape (The wiring on the loom). There are 2 \'knicks\' in the plastic shroud of the wire, and about 2 inches of the wire are not covered in the shield (Similar to coaxial cable).

Here\'s a pick of it. The slash represents where the shielding ends, and the 2 circles show where the 2 knicks are (One knick isn\'t even a knick - it\'s the plastic shroud missing as it has broken). What options do i have!?

(P.S. The pic is a bit rubbish - the camera focussed on the wrong part!!)