Sudden Failure

[2x20V]

Suddenly my AAN engine has no power and can hardly move the car. Took my 1995 S6 on a 360 mile road trip last week. Performed flawlessly. Was a real pleasure driving. Noticed that the plastic bottom shield had dropped real low and was clearing the ground by something like 1-1/2". Dropped it off at the shop the next day after the trip to reattach the shield. I get a call from the shop 1/2 hour later that they couldn't drive the car into the bay - it was no power and is idling very roughly. I told them to try it again in a couple of hours, which they did. They reported it was running very rough but had just enough power to bring it into the bay. Once they were finished securing the shield it had enough power to park the car in their parking lot. I went to pick up the car and while it started and did idle roughly, I was able to start on my way for 20 feet or so but it then it completely lost all power and stalled, and I was stuck in the middle of the road. There I tried to get it going. While it was easy to start there was absolutely no power and the engine continued to idle very roughly and then stall out when I tried to get the engine to move the acr. It seemed to become worst as it became warmer or as any effort to get any power out of the engines was made. I did smell sulfur in the car after trying to get it going many times. The next day the tow truck driver calls me to tell me there is nothing wrong with the car and suggests that it doesn't need to be towed. So I go to retrieve it and find that it is acting the way it did the day before and getting worst the longer I fussed with it. I eventually towed it to another shop that could take the car. They ruled out a blocked catalytic converters - even though they are original - and tried replacing the O2 sensor to no avail. They measured vacuum and found it was very low. No obvious leaks. They are now checking compression. I am looking for any advice of what is likely wrong. The shop is stumped and so am I. Any advice would be appreciated.

[Bowie69]

Sounds like fuel pump....?

[220bhp]

Could be pump or fuel filter even fuel lines so check fuel delivery . I had to replace all on my s6 but, my symptoms where stop then start

[K Simmonds]

I would also suggest a fuel pump that's started to die.

However there's a boost pipe with a ribbed rubber hose that runs under the engine, so if they just pushed the tray back up with out removing it they could have missed a split in that hose which may have been the reason the tray was hanging off. A massive air leak would also explain the car struggling to run.

[newsh]

You need to pull codes with Vagcom, it’s not a magic wand with these old cars but it’s helpful.
It could be bad fuel delivery but IME fuel pumps usually die suddenly and completely.
“Vacuum low” probably means a boost leak. “No obvious leaks” is not good enough. You need to do a proper boost leak test. Pressurise from the MAF hose to 1 Bar, should hold pressure for a while. There's a guide to boost leak testing on here in the stickies.
You also need to find someone that actually understands these cars if you can't do the work yourself.

Actually, try driving with the MAF disconnected, if it runs better that’s a clue..

[Tractor Dave]

All the above first then jumped timing belt. I once had this on a bmw. The belt had lost a tooth.

[newsh]

Yes always a good idea to check timing.

[K Simmonds]

Newsh is right, pulling the fault codes is one of the first things you should do. However after reading your first post again I think you've got a massive air leak. As the symptoms you describe sound very like how my old S2 used to behave if a hose popped off. I very much doubt there's anything wrong with engine so a compression test is going to be a waste of time and money. Get them to remove the undertray and inspect the pipe work. Try and find a garage that is competent working on these cars.

Sent from my SM-A115F using Tapatalk

[Rikki Kitto]

Try and find a garage that is competent working on these cars.Good luck with this most garages are useless unfortunately

[Rikki Kitto]

I had something very similar years ago after limping to a garage it turned out to be the Throttle Position Sensor

[K Simmonds]

I had something very similar years ago after limping to a garage it turned out to be the Throttle Position Sensor

That again is a reasonable suggestion, any shop/garage have and be able to use VCDS, it's take five mins to fit the 2 adapter leads and press a couple of buttons on a laptop.

I still think the undertray was a massive giveaway and it's something to do with the boost pipe under the the car. I may well be wrong but again it would take literally five mins on lift to pull the tray off and check the connections.

[Antsa]

Some very good points here. As said above, if you are not doing any work on the car yourself, you should be looking for a garage that knows our old Audis. Most of the garages don't really know where to start the fault finding on these old vehicles, and when they don't, they do something that doesn't get you anywhere and make you pay whatever they are asking. So best to find a specialist

[K Simmonds]

I know not everybody is mechanically inclined, however when one is running a 25+ year old very high performance car that in it's day was cutting edge it's is a kinda good idea to able to tackle basic job's yourself. Otherwise the potential cost of fixing simple problems can soon stack up into a hefty bill with zero progress.

As a rule problems like this are normally something very simple that with a boost leak kit and a ripped copy of VCDS that one can use at home can be identified and sorted out in very little time. Plus it's always rewarding finding a problem and sorting it ones self, then you know it's been done properly.

Or if you really don't want to get your hands dirty find a shop where at least one of the mechanics is familur with these cars, it will most likely be a VW/Audi specialist but there again it could be someone like me who generally works by themselves in their own shop.

Anyway I forgot to say....

[Rikki Kitto]

[Rikki Kitto]

I didn't realise you was a newby too