Peek at MembersPage/MarcellGal/EngineSwap/AirFeed (idle air section)

The bipolar stepper has 2 coils, that is 4 pins together. Measure resistance between each pair of pins, and document it. Usually 40 Ohm. This rover (?) had 64 Ohm stepper widings.

It is possible to connect the 2 coils in 2 ways regarding the stepper outputs:

The ends of the same coil must be driven a half period away from each other, and A,B,C,D are encoded as 0,1,2,3 respectively.

However, if you reverse one coil, you get reverse stepping sequence. Easy to notice this: engine gets less air as you bump up the mdi.. (forced iac position) during the tests.

This is not easy to measure beforehand, so you have 50% to get it right first. Easy to change config. So 2 config "directions" possible for each wiring (one is good, the other is reverse):

History and LESSON

Unfortunately installer forgot to document this (it would have taken 2 mins when he made the install (when car-back was off), while it took half day to investigate with the car-back on. The car owner apparently doesn't have proper drawings or connect-lists of his engines's, VEMS installers should make sure to leave this info at the owner.