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Hello all,
I have an 88 635csi auto trans with a vin last 7 of 3266761 that I am having a shaky engine at cold start and smooths out a little when reaching operating temps. The TPS I have is the latest style round connector PN 13631708605 or as realoem calls throttle position switch. I cannot seem to find a test procedure specific to this style TPS. The car has no vacuum leaks and I just rebuilt the head and changed all gaskets and vacuum hoses. The car also has all new parts; cap, rotor, ignition wires, silver Bosch plugs, ICV, all new vacuum hoses and bellows. This is my 23rd BMW over the last 25 years. Before I jump into checking the AFM, I would like to check the TPS. I have a Bentley but this TPS does not appear to be covered. I checked this forum but the tps topics don’t seem to be referring to this TPS.
Any suggestions would be appreciated.

The round and the rectangle units are basically the same. You just need the pin outs.The switch should be closed at WOT and idle. This is the E34 M5 unit diagram.

Thank you. Would you have the procedure for the M5?

The image below is off the bentley manual for E28 / 1988 535i which should be the same. There is no image to the round connector TPS in the Bentley and that’s why I am in doubt. I am just going to “assume” that’s the right pin out and just run the diagnostic . Thank you

1988 TPS diagram and plug pin out. Note that your picture above seems to be of a later model ?

you almost certainly need to reset the throttle butterfly and then the TPS, in that order, according to procedures described in the manual.

The throttle body linkage wears over time and this results in the butterfly being too far closed at idle, even though nothing has been adjusted. The ICV ends up being wide open when the engine is cold and worse yet as you come off idle, there can be a huge flat spot/near stall too. If you reset the TPS without resetting the TB, you get a whole new range of symptoms.

BTW the potentiometer part of the TPS only reports to the gearbox ECU and doesn't affect engine running in any way.

cheers

Thank you guys. I will do the adjustments over the next long weekend and report my findings. As Bruce suggested, I’ll make sure the throttle body is adjusted first (checking for plate gap/ adjusting cable) followed by the TPS. I will most likely check for closed, partially open, and fully open from the 2 ECU Pin connectors as indicated in the diagram. Thanks again.