I spent some time contacting local salvage yards trying to scavenge a BMW throttle position sensor vTPS (ref:
) without any luck.
I ended up buying one online. It is a BMW replacement part. (#13 63 1 402 143). As it turned out it needed some fabrication and modification to fit..
first things first:
-The intake valve half moon rod fits in the sensor, but since there's no hole for the rod through the sensor (the hole for the rod is just a socket, it wont feed all the way through), it now sits at a distance from the throttle body, where its hard to fasten it.
-The stock TPS harness fits the new sensor connector, but the wires to the pins needed to be changed.
-The vTPS operates on 5 volts (as it should with megasquirt)
I checked with a ohm-meter what pin in the vTPS outputed the TPS signal.
Measuring resistance between the different pins while adjusting the variable resistor, revealed that pin 2 relays the tps signal.
The miata '91 wiring diagram
shows that pin 2 in the harness is ground.
I cut up the wiring going into the harness and switched LT GRN-WHT and BLK-LT GRN.
RED still provides power
I resoldered my jumpers in the MS DIYPNP, per the wiring diagram and the online instructions. VREF to 1N, TPS SIG to 4N.
Here is how the new TPS sits with a new plate with threaded (4mm) holes for the new sensor.