I noticed an unattached wire dangling below the intake manifold and found a terminal on the nearby knock sensor that had corroded off. It's probably been off a long while, and the car runs so fabulously that my first thought was to ignore it.

2nd thought was that it's there for a reason and I started shopping around. The sensors for 83 to 88 240s go for around $140. while the 89 to 93s can be had for $30. which made me pause. The older sensors are metal with an integral stud and one wire, while the newer ones are plastic with a bolt hole and have 2 wires, one being a ground. I'm assuming that the older ones grounded through the block.

My question for anyone with knowledge of how these things work is can I use the newer sensor as it looks like it will bolt on using the existing stud hole. I can easily run a ground wire to the 2nd terminal. I dissected the old sensor and there's really not much there. Correct me if I'm wrong, but I'm guessing there's a continuous current running through the sensor, and the knock interrupts the current which is the signal sent to the computer. I'd like to save a few bucks, but I'm also curious if three's a difference in the signal sent by the two versions.