5 replies to this topic

[Snoop Deville]

Hi gents,

Pretty good at mechanics, new to mini's, but hit me up with the tech talk, I don't mind

New to me '93 mini SPI.
Runs fine, except when hot the idle will rise too much (no tach but suspecting approx 2krpm)
did not do this with the stepper motor multiplug disconnected (was that way when bought)

however, I can't see the stepper motor move.
It will click, rattle, but not move its pin.

I've fully disassmbled it, and when the ECU actuates it, it will just vibrate, very quick clockwise-anticlockwise motions, but not rotate.
It's however not stuck, when not powered I can easily turn it by hand.

I've measured resistance on all 4 pins to the common, they all read exactly 14,3 ohm.
I've measured through the cables from the stepper multiplug to the ecu multiplug, all have proper connection.

I'm unsure of the location of the "idle screw" (I know it's not an idle screw, but you know which one I mean) due to suspicion of the previous owner tampering with it to get "proper" idle with stepper disconnected. this however should not matter when I've the stepper in my hand ...

Now, what's at fault? the stepper motor itself? the ECU? Some coolant sensor playing up in some weird Rover way? (yeah, I usually do Land Rovers ... )

What's the procedure for testing this? Haven't been able to put my hand on an SPI shop manual ...

Thanks,
Quentin

[icklemini]

one quick way of testing the stepper is:
1) ignition on
2) under the bonnet - operate the the throttle fully 5 times...
3) stepper should move...

[Snoop Deville]

Icklemini,
thanks for your reply, but I know it's not moving, and that it's trying to move (as it's obviously getting power to vibrate)

However, what I want to establish, is if the ECU is not giving a correct signal for it to move, or whether that signal gets lost underway, or if the stepper gets a proper signal but can't act on it (ie. is broken internally)

Any clues how? Don't have a spare ECU nor stepper around, yet, which would obviously make things easier ....

[Ethel]

Isn't it the same as K Series single point? You could look for a Metro in the scrappers.

http://www.imagesco....stepper/03.html


4 wires suggests it's a unipolar motor - 4 coils (earthed via the controller), 1 common supply

[tmsmini]

Sprocket had some excellent pictures with diagnosis info in a thread at one time.

The pinned thread has a little info, but it sounds like you have those aspects covered:
http://www.theminifo...showtopic=49801

[icklemini]

I would suggest the stepper has gone...