405 stepper motor connector

My 1995 petrol 405 cuts out at low revs. But it's very intermittent so I'd like to check that it's not a bad connection on the wiring to the stepper motor.

So does anyone know where on the engine, or whatever, I might find the stepper motor connectors. I have the Hayes book, but they don't show that piece of info.

Thanks.

Reply to
Tim
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Tim, You don't say which engine you have but on my 1995 405 with XU7 engine the stepper motor is right on top of the engine just to the left of the coil pack. It has two hoses about 1" diameter connected to it and the electrical connector is on the rear of the unit as mounted.

HTH

Bob

Reply to
Bob Minchin

Could this be the same for my N reg 405 auto estate ( petrol) ?

just cuts out at low revs, restarts ok, then may cut out again and again , lasting for anything from 10 minutes to a day, but then will not return for

2 to 3 months ?

David

Reply to
David Hicks

Interested because I once had a 405 petrol (now have diesel) that sometimes cut out for no apparent reason: what is the stepper motor and what does it do? Thanks

Reply to
Wichita

Bob - many thanks. The car is a 405GTX estate and the engine is an XU10 (1998cc.) The connector you mention doesn't seem to want to come out so I've given it a good wiggle and we'll see if that fixes it.

Just in case there is a connection, I should mention that the car also shows a couple of other faults: the STOP light comes on, with the temperature guage red light on, even when the car is just about stone cold and the temp guage is reading minimum

- the fix is an emergency st>> intermittent so I'd like to check that it's not a bad

Reply to
Tim

Tim, Are you familar with removeing the engine elctrical connector on your Pug?You will see a metal wire spring loop around the connector which need to be compressed to withdraw the connector.

I doubt if your temp light/ stop problem is related to the flasher observation.

I recently had cause to remove the thermostat housing from my engine only to find thet not only did it have three separate temp sensors but also it had provision for a fourth. I looks like at least three systems need to know the temp and do not talk to each other!! I think I'm correct is say that the temp gauge sensor becomes lower resistance as the temperature increases. I could well be that you have an intermittent short circuit in the wiring or gauge thus indicating very hot irrespective of the actual temperature. Any one of four events will light the STOP light Over temp water. no oil pressure and two other things I cant recall

I strongly suspect your fault is an intermittent short which is 'cleared' by the deceleration when you slam on the anchors.

As for the flasher problem, I don't know but several posters to this NG seem to have flasher oddities and I suspect they are also intermittent connections.Try a wiggle and clean up of the relay contacts. Pugs generally have a poor record of electrical connections.

hth

Bob

Reply to
Bob Minchin

A stepper motor is a motor that rotates a small fraction of a revolution in one direction or the other when a small electrical pulse is sent to it. When no pulses are sent, the moter is held stationary by the act of the magnetic field In this application, the stepper motor adjusts the amount of air that is allowed to bypass the throtte. ie it allows the ECU to control the idle speed of the engine once you have taken your foot off the accelerator. By sending pulses from the ECU to the stepper it can make small changes in the amount of air allowed into the engine, measure the engine speed and then check if it needs to make a further adjustment and so on until the idle speed is just right.

This link http://209.41.165.153/stepper/Tutorials/UniTutor.htmwill probably give you more information than you want/need about steppermotors.

HTH

Bob

Reply to
Bob Minchin

Just adding to the explanation Bob gave... My 1952 BSA Bantam had an adjustable screw on the carb which would set the tickover speed. Quite probably this was also used on cars until emission control regs came in. My understanding is that the stepper motor (in reality just one of many stepper motors in a modern car) is an automated version, controlled by the ECU, of the screw on my Bantam.

Reply to
Tim

Hi,

No, the stepper motor brings an extra amount of air to the engine, this replaces choke. AFAIK (correct me if I'm wrong) it doesn't act once the engine is warm. You're talking about the idle screw here, if I understand correctly. The idle is automatically managed by the ECU. and is a different thing (you can consider the stepper motor as a bypass on the air intake / throttle body assy - where the idle settings are). At least it was the case on older ECUs (Bosch Jetronic series. Ok, I know we're talking about Motronics or some crappy Marellis here).

Regards, G.T snipped-for-privacy@worldonline.fr

205 Diesel & turbo-Diesel :
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Reply to
G.T

Because this will be archived, I should add the final diagnosis...

The connector is where Bob described and plugging and unplugging had no effect. The dealer cleaned out carbon dust from inside the stepper motor and, so far, that has done the trick. Didn't cost much.

Of the other problems I raised in a follow-up post, the temp warning light seems to have been caused by a slightly low coolant level (!) and the tick.tick.tick from the flasher unit remains undiagnosed - it went away when taken to the garage ;-)

Bob M>> intermittent so I'd like to check that it's not a bad

Reply to
Tim

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