Trouble?
 

On the way to work this morning, the ABS lights came on and then I noticed that the car had no 'oomph'. The revs seemed to climb, the engine didn't respond to the throttle.

It felt a bit like it was in limp mode, but the gear lights weren't on and it was apparently changing gear OK.

Any ideas?

no idea but first thing would be to plug the car into VCDS and do a full scan.

Similar symptoms to my ongoing problem, though mine happens "randomly" (or not) and there's no ABS light.
Mine always clears with a throttle "blip" (off/on), how did yours?

Sounds like what I had a couple of years back. If I'm correct, it was the throttle position sensor failing, sending dodgy signals to the ECU, and the car going into a sort of limp mode - throttle flat to the floor, and only a hint of acceleration, and ABS light on. Turn off and on again cleared it a couple of times, but I ended up getting towed from just off the M6 North bound when I started panicking that it was gearbox related and lost my bottle.

Had it replaced at Audi in the end.

Z

Expensive?

I had a similar problem a while ago too, but in my case it was the ABS pump.

As I understand it, you'll get the loss of power symptom with most ABS faults, since the traction control makes the assumption that a wheel may be slipping and therefore limits the power.

In my case, the fault was very intermittent at first, but (from memory) it would usually put the ABS light on, which remained on until cleared, by turning the ignition off and on. Sometimes it wouldn't happen for days or weeks; other times it would happen several times in one day. Eventually the fault became permanent.

When the pump was diagnosed, I assumed they meant the pump built into the ABS controller unit under the bonnet, but it turns out there's a separate pump on vehicles with ESP, hidden away behind the n/s front wheel arch (I think).

Not sure exactly how much the new pump cost in the end, but it wasn't cheap; 2 or 3 hundred quid at least I think.

A8parts have a throttle position sensor at £25.99 and ABS pumps starting from £110, although as HP says, it's sounds very similar to the fault he's had for ages, which I've also experienced a few times as well, but no ABS light.

Can't remember....it wasn't peanuts at Audi main dealer though...

I'll check when I'm back home later in the week.

Z

Jim, is ABS light still on?
What VCDS is saying?

Any idea where that actually fits and how easy it is to swap?

It appears to be attached to the throttle body by two screws. The best picture of it I could get was here:

http://www.audiforums.com/forum/audi...5/#post1082894

Not sure how easy that will be, as no way to guage 'actual' position.

Well, by the time I left work, the ESP had gone off and the power was back to normal. The ABS, EMS and another (yellow triangle) light were still on though.

I called in to A4 Audi and got a diagnostic scan. It was the throttle position sensor and Andy cleared the other lights, which have stayed off.

He thinks that it's water getting into the switch/connector above the throttle peddle and, if I search my ageing memory, I seem to recall the same issue a couple of years ago. I'll need to get a closer look when I find the time.

So that's the pedal position sensor, not the throttle body sensor?

Yes, I think so

Yes - mine was the pedal position sensor - fits down above the pedal box...sorry for the confusion.

Z

That's what I'm beginning to suspect on mine, how easy to fit and how much are they?

It will require removing the lower dash trim under the steering wheel and I suspect also the air vent tunnel, so you can get access to the top of the pedal box. It's held in by two bolts (number 6 in the image).

After fitting, you then need to adjust it, and will need VCDS to do it. I've attached an image of the culprit and also the adjustment instructions.

The one on mine has the part number 028 907 475 BD ('01 3.7), diesel ones are BC, but can't confirm if all the petrol ones use the same part. Used one on eBay range from £46 (from A8parts) upwards.

Thanks, A8parts show the one they have (BD) as being compatible with a long list including S8.
I'll plug in VCDS and check the measuring blocks. I "thought" I'd done it before but I suspect I did the throttle body not the pedal. :o

Update on mine:

Car ran fine from Monday evening, through absolutely torrential rain and sleet on Tuesday and Wednesday and then, towards the end of my commute this morning, which wasn't that wet (and after sitting in my garage all night) same fault.

ABS, EPC and ESP lights on and no 'oomph'.

So, my current thinking is that it's not water ingress, but more likely the increasingly frequent, intermiitent fault on the sensor that Zip describes.

Planning to book it in to have this, cambelt (and ancillaries), brake fluid change and headlight washer done.

Gonna set myself up as a registered charity and/or remortgage the house and/or sell the kids into slavery! :-(

I was plagued with the very same problem recently. It took me months to sort it and as always I looked at the most expensive items first. I changed practically everything including the throttle position sensor and the throttle body. It turned out to be the fuel pressure regulator and a broken wire in the throttle body cable. The solution is sometimes not the most obvious.

Jim, rather than go O/T on the 'MoT Time Today' thread, can you confirm which sensor you got replaced? Was it the throttle position sensor or the pedal position sensor? If it's the PPS, I might consider trying a second hand one from our forum sponsors.

Oh, sorry Sean, I missed this question. I was told it was the throttle position sensor, but I'm not certain. The receipt just says 'sender module', but I'll give them a call to find out and get back to you.

It's well worth a mention that the whole car is transformed as a result though.

Ever since I bought the car, the fisrt gear change up in a morning was a bit clunky (even after the gearbox services) and occasional other changes were clunky too. Nothing major, but noticeable.

And I always thought there was a hint of a misfire when I put my foot down at already high motorway speeds. But I never saw a misfire report on VagCom and the eventual removal and replacement of the stuck plug did nothing to improve it.

But now, the gearbox is as smooth as silk and the general response of the car in all types of driving is transformed. And there's not a sign of the 'misfire'.

It's made a heck of a difference! :)

So, apart from the very obvious intermittent fault with the dash lighting up and the power control coming on, I suspect that these things wear gradually before they fail. It was an expensive part, but I'd spend the money again happily (but I wouldn't risk a second hand one).

I'm equally interested......

I phoned the garage this morning and am awaiting a return call. I'll post as soon as I hear back.

It was the throttle pedal sensor module, part number 02 890 747 5BD (although that looks a strange number to me). And the part was £325! But worth it IMHO.

Thanks, I guess we now have to see who takes the plunge first and follows your lead.
Any idea how difficult this is, i.e. DIY or not and how many hours a garage would charge?

This link gives alternate Bosch part numbers such as 0280752022: https://eurochopshop.com/shop/a8-s8-...0-00-01-02-03/

I don't know how difficult the job is. Mine was done at the same time as the cam belt for a total of £164 + VAT for labour

Already answered. See post on previous page:

http://forum.a8parts.co.uk/showpost....6&postcount=17

Sorry!

http://www.recreateweb.com.au/wp-con...mputer-doh.jpg

So who will be first to take the plunge?

Cold weather and arthritis say probably not me, at least DIY.
I need to book the car in to investigate some knocking noises when cold (suspect catalyst or exhaust mountings) so I might get the part from our sponsors first and ask the garage to do it.

Maybe we should check price and availability first?

Jim mentioned the price earlier (£325), which is way outside my price range, so I've opted to 'try' the cheaper option first... our sponsors.

Having said that, cold weather and an extremely short fuse at the moment won't see me go near the car with tools :)

Will add it to the 'To Do' list when the weather improves.

Me too, I've sent an email this afternoon.
Better see what the price is and how many they have to avoid an argument! I'm definitely not going into a bidding war for the last one. :ROFL:

Well, I've been on eBay and made an offer for one, which was accepted. They may have others in stock that aren't listed on eBay.

I bought a second-hand instrument cluster a few months back, but phoned up about it so that I could get one with a mileage that was close to mine. That's another 'To Do' job, but that will have to go to the dealer to code the keys in.

Will just add this box to the others I have for the car.

I looked earlier but didn't see one, sure you got the right thing?
I can only see one in the USA for about $200.

Yes, the code that Jim listed is the same as the one I posted in post #17. I just remove the spaces when doing a search for it. Only thing to ensure is that it is a BD one, which is for petrol, and not the BC one for diesel.

As I may have mentioned elsewhere the knocking noises (loud!) are the catalyst, and it needs doing PDQ.
The hesitancy symptoms have got worse in recent days so I'll get the catalyst fixed first to see whether or not it's a factor.

I have also acquired a throttle pedal sender potentiometer (from our sponsors of course :cool: ) but will hold off on fitting that for now.
There are references online suggesting that the throttle BODY needs recalibrating (I have done that before while investigating this) after changing the pedal or sender (not 100% sure why) but is there any need or method for calibrating the actual sender on the throttle pedal (I can find nothing about that) or is it effectively "preset" at manufacture?

I drove my S8 without the OS cat for a few months. Wont hurt anything other than emissions. It was only when i changed it did i realise quite how bad it was - it was hollow, over time blew the monolith out the rear. :ROFL:

It could depend on age; mine is the later type with post-cat lambda sensors and I guess the readings from those "might" have an effect.
Either way, I normally follow the "only change one thing at a time" philosophy when trying to resolve problems. :cool: