I have an 89 B230E k-jet (non-US market). It has no lambda, no catalytic converter and it has a knock sensor. Strictly speaking the car is a 740 and I should be posting in the 700 column but I find that most of the k-jet gurus residents are here.

Anyway, I have this knock which occurs above 3000rpm. Using the highest octane gas available here and also trying different brands have no effect. This knock has been there for quite some time. I suspect the knock sensor is faulty but how do I confirm it's not working on a k-jet? With the 700 (non-B230E of course) and 900 series there's the luxury of error codes but not with my B230E.

I've taken out the knock sensor and it looks fine from the outside. The connection to it is good. Looking at the wiring diagram in Haynes the sensor is hooked up to the ECU. I didn't bother checking the connection at the ECU end as the car is running fine except for the knocking.

Appreciate any advice. If it wasn't for the fact the a new knock sensor here cost nearly $200 (local currency) I would have just swapped in a new one. That option I'm keeping last.

Thanks in advance.