Changing a Mk1 VRS knock sensor

[David 8]

Right, all sorted! I slackened it off for a while, then re-torqued to the correct 20Nm, and magically no more error code popping up on my test drive route as it has three times in the last two days. Also I was getting a flat spot at high revs under load. For example at 120mph in 5th it felt like it was hitting a wall in the power, and the power just ended. Now sorted, and the car feels noticably faster. So a note for future DIY'ers, torque the knock sensors to exactly 20Nm, or they won't work properly!

Part numbers:

Knock Sensor 1 (G61) is 030 905 377C @ £45.57+vat rrp

Retaining bolt is N01033520 @ £0.42+vat rrp

Note that the original sensor was made by Siemens and had a steel core, the new one was made by Bosch and had a copper core (both parts under identical part numbers).

Let the DIY begin!

This is where it's located (removed here). It's the non rusty hole to the right of the 'stat housing:

Once everything is disconnected, I find holding it all back with zipties works well:

Bosch vs. Siemens. I think the Siemens one failed due to corrosion. Looking at the patent for the Bosch design they are pretty sensitive things.

New sensor fitted and plugged in:

Here is the patent for the Bosch knock sensor: http://www.freepaten...com/5398540.pdf

It explains how it works, and what all the internal components are. Pretty interesting.

The only problem I came across was myself not following the instructions! I think I was lucky to have not damaged the sensor, and managed to get away with it this time. Hopefully this thread helps lots of people googling this problem!

Case closed!