FIXED THE ERROR MOVEMENT PISTON PROBLEM VISCOMATIC!

[alfa164superwebmaster]

Dear all,

As you could have read in my previous posts, I was struggling with the dreaded 'Error Piston Movement' problem after the rebuild of my Q4. Also with my previous Q4 i was facing this problem.

I tried to bleed the system with the Alfa Tester MA12A module numerous times, without success.
Als the Course Piston Parameter (piston movement) stayed at 0%, no matter what I tried.

So I decided to try to actuate the solenoid by hand, to see if the piston would move when controlled manually.
To do this, I purchased a PWM controller from Conrad.
The type I used was a Kemo Power Control M171 DC 5A

I connected the PWM controller to the solenoid on the viscomatic unit, and a 12V 2.5 A power supply from my wifi modem
When running the engine, I turned up the potentionmeter of the PWM controller.

After one or two full power settings, I hear a slight 'clunk' at the diff and I got 100% piston movement on the Alfa Tester!!
Disconnected the PWM controller and reconnected the Viscomatic ECU to the solenoid.

Everything now works like a dream.
So it seems the Viscomatic piston got stuck from standing still (car stood for 4 years).

The PWM controller is very handy for debugging the Viscomatic, so I hope this helps the Q4 drivers out there.
Pictures are attached.

Cheers!

Viscomatic PWM controller 1

Viscomatic PWM controller 2

Viscomatic PWM controller 3

[Alfan]

Awesome!!!!!!!!!!

That is great work and thanks for sharing the info

[AlfaWhiz]

Great result!

Very glad to hear that you've fixed it, well thought out method. Good to have this trick on the sleeve as many of us had or still have this issue.

[164 TD]

Still wondering what part of the gearbox the actual piston is. You can see the viscomatic coupling plates very clearly, but the piston that "squeezes" the viscomatic plates and the piston that actually mechanically connects the inputshaft to the viscomatic are hard to determine.

[AlfaWhiz]

The piston is actually visible on the picture above, just left (or more towards the input shaft) of the Viscomatic coupling discs. It's drawn as a cutaway and you can see some of the void compartments where I believe the hydraulic fluid is actually acting on the piston.

visco_piston.JPG (23.28 KiB) Viewed 16958 times

Here you can see it even better, its from the Steyr Puch or Magma Steyr documentation on Viscomatic:

Now after picking my car from the workshop where it sat for a while I seem to be facing the exact same problem. Error is bad piston movement and piston stays at 0%, Viscomatic is disengaging immediately after the throttle is pressed. I've tried to clear the code multiple times even when driving, counting that it would maybe warm up and start moving, but it looks that I'll be testing your new method with the PWM controller soon.

@alfa164superwebmaster can you post the details of how you connected the PWM to the actuator? Did you run an extra long wire from the cabin to the underside of the car or did you work from below the car? Which cables of the PWM module go where on which connector on the car? I know it's rather straightforward but would prefer not to make things worse...

Many thanks in advance!

[alfa164superwebmaster]

Hi,

I am on holiday for one more week, will send the info as soon as I get back.
The basic idea is that the PWM controller is hooked up directly to the solenoid (the big one at the back, with the 36mm hex fitting).

As a power supply I used a 2a 12v power supply from my wifi router Just to ensure there is not too much power so the solenoid will blow up.

Just start the car, let it idle, connect the PWM controller to the solenoid and turn the potmeter dail up and down a few times, you will hear the hydraulic lines and fluid moving (hard to describe, but you will know).

After a few (3-4 times) turning up the dail, shut down the car and reconnect the solenoid to the cars wiring.
Start up and all should be fine.

Good luck!

[AlfaWhiz]

If you could post the details of wiring the PWM to the solenoid it would be great. I will attempt the fix soon, as my Viscomatic piston is still "stuck".

I've meanwhile located a spare 12V power supply, only 1A but should be fine I reckon (better safe than sorry). Will be trying to buy a suitable PWM (or the same one you've used) this week.

I'll be happy to report progress to confirm the fix and boy do I hope it will work for me as well.

Cheers

[Alfan]

Looking very much forward to your results (and photos of it), as this is still on my to-do list

[AlfaWhiz]

I will be wiring it all together shortly, waiting for the PWM module to be delivered now.

Can you tell us how did you wire it to the proportioning valve? Looking at the diagram, I see only 2 pins there (http://alfaromeo164register.com/manuals ... age_03.jpg), but I believe there are 3 in reality.

Hoping for a simple from-to explanation between the PWM and the connector on the proportioning valve. I see some of it on your photos, but would really like to make sure and minimize the risk of frying it.

Also, what connector type/plug did you use to attach to the valve? I believe it's a Bosch JPT 3-pin but am unsure.

Thanks.

[Alfan]

Whatever extra information is available on this, I am still interested. I think mine needs to have this done and most likely another Q4 in the area needs the same treatment - and I better start doing something on this...

[Alfan]

I also hope that the photos will be available again after the site update

[Alfan]

I have ordered the PWM unit, and found a printout of the photos from this thread. When looking at it, I believe the connections should be like the attached, I made. Comments would be appreciated

Q4 flow valve test

[AlfaWhiz]

I was pretty sure I already responded to this thread before - it did work for me!

Your connection diagram seems right, there are only 2 wires on the valve so hard to mess up.

I did a few cycles and heard a knock and it started working fine again! One note is to use correct power supply. At first I tried with 1 Amp but it wasn't enough. 2.5 Amps worked fine. Remember, no more than that or you risk the valve!

Fingers crossed

[Alfan]

Grazie

[AlfaWhiz]

Oh one more thing, I did it while having the FL tester with MA12A plugged in and watching piston position % parameter. But now I don't remember if it was helpful to watch the tester or not

[Alfan]

As long as I hear some kind of 'klonk', I guess it is going as intended...

[alfa164superwebmaster]

Haha cool, nice to see good results )

Mine also still works great!

[Cavallino]

Why am I not able to view the photos in this thread?

I currently have the 4WD error light illuminated my instrument cluster, so I am awaiting an MA12A module and FLT to diagnose the issue. I'm hoping it's an easy fix, something like this.

But I can't see any of the photos, or understand exactly what was done, or how?

[Alfan]

This site was updated some time last year and not all photos have been recreated. That is also why my photos of the inner tie rod had disappeared.

If you write a PM to those who put in photos, they might still have them and could be able to add them to the thread again...

Good luck with the diagnosis, looking forward to knowing about your findings