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TPS Test / Adjustment for a 1988 Auto 635csi

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abouzmm
Posts: 4
Joined: Tue Nov 04, 2014 1:59 pm

TPS Test / Adjustment for a 1988 Auto 635csi

Post by abouzmm » Mon Jan 14, 2019 12:38 am

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.
Attachments
63713678-F426-4172-B739-79D12246E586.jpeg
63713678-F426-4172-B739-79D12246E586.jpeg (16.49 KiB) Viewed 334 times
88 BMW 635csi Auto
VIN 3266761

baders
Bigcoupe Contributor
Posts: 958
Joined: Sun Nov 23, 2014 7:38 am
Location: Perth Australia

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by baders » Mon Jan 14, 2019 1:32 am

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.
TPS.PNG
TPS.PNG (24.86 KiB) Viewed 329 times
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers

abouzmm
Posts: 4
Joined: Tue Nov 04, 2014 1:59 pm

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by abouzmm » Mon Jan 14, 2019 1:58 am

Thank you. Would you have the procedure for the M5?
88 BMW 635csi Auto
VIN 3266761

abouzmm
Posts: 4
Joined: Tue Nov 04, 2014 1:59 pm

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by abouzmm » Mon Jan 14, 2019 2:13 am

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
Attachments
736E9482-02FB-4319-B88E-FD7956329EA2.jpeg
736E9482-02FB-4319-B88E-FD7956329EA2.jpeg (1 MiB) Viewed 328 times
88 BMW 635csi Auto
VIN 3266761

baders
Bigcoupe Contributor
Posts: 958
Joined: Sun Nov 23, 2014 7:38 am
Location: Perth Australia

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by baders » Mon Jan 14, 2019 11:17 pm

1988 TPS diagram and plug pin out. Note that your picture above seems to be of a later model ?
throttle switch 2.PNG
throttle switch 2.PNG (73.27 KiB) Viewed 308 times
throttle position sensor pin out.PNG
throttle position sensor pin out.PNG (41.97 KiB) Viewed 308 times
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers

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Brucey
6 Series Guru
Posts: 9949
Joined: Fri Apr 09, 2004 7:17 am
Location: Cambridge, UK

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by Brucey » Mon Jan 14, 2019 11:47 pm

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
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

abouzmm
Posts: 4
Joined: Tue Nov 04, 2014 1:59 pm

Re: TPS Test / Adjustment for a 1988 Auto 635csi

Post by abouzmm » Tue Jan 15, 2019 2:47 pm

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.
88 BMW 635csi Auto
VIN 3266761

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