ABS speed sensors and ISV for Audi RS2

[JonRS2]

Hello.

I am struggling to find the following parts for my 1995 Audi 80 Avant RS2:

2x Front ABS wheel speed sensor (893927803A)
2x Rear ABS wheel speed sensor (8A0927807C)
1x Idle Stabilisation Valve (034133455A)

I don't think the garage looking after my Audi RS2 has VCDS / VAGCOM.

Problem: ABS activating when coming to a slow stop (boing noise from brake pedal).
They think that one of the fitted wheel speed sensors is faulty but don't know which one.
I am told that it will be a case of removing one; fitting a replacement; see if that is the solution; if not, remove second one; fit a replacement, etc. but cannot reuse existing sensors once removed.
So, I may need four new ABS wheel speed sensors.

Problem: hunting idle when engine is warm (e.g. when stopped at traffic lights during a long drive).
They think it may be the ISV (there are no boost leaks from a smoke test).

Any pointers to where I can find these parts gratefully received.

At this point I wish I had purchased VCDS / VAGCOM years ago.
It might have saved me ££££ over the years in time spent diagnosing the cause of problems / purchasing parts that may not be required...

[hashluck]

This is ISV Part No. 034133455B which I think RS2 uses rather then the A version

https://www.ebay.co.uk/itm/263712154615

You can also clean an ISV but the new ones are cheap enough to warrant replacement

[K Simmonds]

If the ABS light comes on and goes out as it should do and the Auto Check is happy I doubt you need to go through the hassle and expense of changing all four sensors... To test them check resistance of across each sensor with a multimeter, I can't recall what value they're supposed to be off the top of my head but if one is wildly different to the other three than that's the one at fault... I may have a couple of good fronts spare but no rears I'm afraid. However, from the symptoms you describe it sounds more like one of the ABS rings on the CV joints is either heavily corroded or damaged in some way.

The S2 I worked on recently had a duff ISV, idle all over the place, hunting and stalling when coming to stop etc. Try unplugging it, the car should then idle okay but slightly too fast and may occasionally stall when coming to a stop but will be much better to drive than with a totally dead ISV. They normally respond well to cleaning with brake cleaner then lubricating with a couple of drops of the cars hydraulic fluid, I tried cleaning the one I mentioned three times to no avail so gave up and fitted a good second hand one. If you need a new one they're not expensive as Audi used them on a lot of different models from the 1980/90's, my back up spare got used on the customers car so I'm afraid I can't help with a second hand one.

Having VCDS is pretty much essential IMO when running one of these cars, well worth investing in, takes most of guess work out of fault finding and it works on all pretty much all VAG cars with OBD 1 or 2 connections. I've got a Rosstech VCDS cable and adapters from 2015 and have used it on cars from as early as 1987 to date after I updated the software which is free once you've made the initial purchase. If you only want to use it on your RS2 a ripped copy will work perfectly well, though the quality of the genuine cable and and 2x2 adapter required for OBD 1 cars like the RS2 is considerably better. It's quite easy to get the polarity backwards with some of the cheap knock off 2x2 adaptors which will kill the cable, this is basically impossible with a genuine set up.

[JonRS2]

Thank you both very much.

I will hopefully hear more from the garage tomorrow.

The latest I had heard was that a new ISV and one or two new rear ABS wheel speed sensors had been sourced but not fitted yet.

The existing ISV was cleaned but that wasn't sufficient.

The drive shaft pick-up rings / reluctor rings / tone rings were checked thoroughly but found to be OK. I think all the CV joints were checked too.

I am not sure why the resistance of the sensors cannot be checked with a multimeter, but I was told that isn't possible as the sensors will not go in any further / possible gaping issue / cannot identify which one is at fault (?).

Would VCDS likely have shown which ABS wheel speed sensor is faulty?

I don't have a Windows laptop, so would need to invest in: (a) a Windows laptop with an operating system that works with VCDS, (b) whichever VCDS is most appropriate (VCDS-Lite or VCDS Enthusiast?), (c) the correct VCDS cable, and (d) the correct 2x2 adapters. As mentioned, I wish I had done this years (decades?) ago as it may have saved me ££££ over time. Presumably, the more expensive the VCDS (e.g. Enthusiast over Lite), the more detailed information it provides on fault codes?

I was unable to see anything helpful on the Auto Check (where the OK usually appears) as it has recently been showing that the washer fluid level needs topping up (even though the washer fluid bottle is full). Presumably that is a faulty washer fluid level sensor or faulty washer fluid pump? Anyway, with that washer fluid level symbol appearing, I couldn't see other Auto Check symbols. That should be resolved in the coming days.

My RS2 could do with a NSR wheel arch liner in very good condition too (the existing one still fits but is not in as good condition as the other three wheel arch liners - I have no idea why).

Other than that, it's all fine!

[JonRS2]

PS: a "clonedropzz" sent me a Message through S2 Forum Messages at 17:17 this afternoon.

Is "clonedropzz" a Member on here, or is it a bot / hacker?

[K Simmonds]

I forgot to mention it's essential that the ABS sensors are pushed fully home into the bearing carriers otherwise the ABS light will normally come on when over 20MPH and the system may do odd things like you describe. To test the resistance of each sensor simply unplug the connectors in the engine bay for the fronts, the rears are under the base of the back seat and use the the two prongs of a multimeter to get a reading across the connections. This is done with the car stationary and polarity doesn't matter, 1.7 Ohms or thereabouts rings a bell but like I say if one's duff it'll be obvious compared to the others.

About 25% of the time it's possible to extract and refit old ones without any drama, though very often they're a complete pig to get out if been left undisturbed for 30+ years and end up being destroyed during extraction. When fitting new ones the bore in the carrier needs to be totally rust free, ideally use new brass guide sleeves though good second hand ones will do, again they need to be clean. Give the bore, sleeve and sensor a coating of copper grease making sure to leave the tip clean and they should be easy enough to pop in and out in future should you need to. I can normally remove the ones on car's I've fitted ones to by hand after pulling the dust boot back and leaving them soak in WD40 or the like for a couple of hours, if not I've got a pair of soft jaw grips I use to get them moving which does't damage them.

I'm pretty sure it's possible to use VCDS to do basic check of the ABS system on ABY S2's as well as RS2's which should tell you which ones at fault, I know it's not a feature on 3B cars so could be wrong. To be honest I've never needed to use VCDS on the braking system of a B3/4 car, though I've used it on B5's and newer models quite often where one can see live data and watch what each sensor is reading with the car on the move. I'll put a battery on my car over the weekend and check what it communicates with and to what level, I've been meaning to for ages so no problem

HEX-V2 VCDS (which is what you need) has the same capability's whatever version you go for, it's the number of different VIN's you can use it with that varies. You can use a dongle and a smart phone but that's really annoying to see properly when viewing live data. I use a Windows 10 laptop which cost £50 off eBay with mine which is the old version of the HEX-V2 professional kit that can be used on unlimited cars. The basic three VIN HEX-V2 cable is $200 and the software and their fool proof 2x2 adapter is $50 so you could set up for well under £300... You can of course get a ripped version and cables for much less but IMO it's worth spending the money on a genuine set up, or consider going second hand from eBay. You still get support from Rosstech for life as long as the cable is real.

https://www.ross-tech.com/vcds/interfaces.php

I've also been getting messages from various random new members when posting in the wanted section, I presume they're scammers.

[Crasher]

The type 8C 80 Quattro Avant rear wheel arch liners are notorious for falling apart. Klokerholm make some thin copies that are made from thermoplastic rather than thermosetting plastic. The hole positions are marked relatively accurately so mounting at one screw point, you can use a hair drier (or hot air gun on a low setting) to warm the plastic and gradually work your way around the liner, mounting it one screw at a time until, gently pushing the soft plastic into place and holding until it cools, moulding it tightly to the shape of the inner wing, I think I have some pictures at work. I wear some thick gloves whilst doing this and take care not to get the plastic too hot as you mar the finish but on the ones I did, I didn’t like the plastic finish anyway so I Raptor coated and then painted them RAL 9005 satin black to make them thicker (better sound absorption) and too look more original.