Raoul

I can't figure this one out. My A4 1.8T doesn't smell hardly at all when cold, but the A6 is almost unbearable. I'm thinking it must be the cats since it has 2 vs. 1 on the A4, but with 60k I wouldn't think the cats would be a problem. Any ideas?

Suds

Bad fuel pressure regulator can sometime cause the smell but that would usually set a code somewhere...

Did you or previous owner ever drive with a blinking MIL -- that means raw fuel dumping into the cat and it could have been poisoned... dito if there is a lot of misfiring...

screwynewy

I'm sure that someone else here could tell you more specifically what happens but that is the basic reason that the exhaust smells different. My 4.2 does the same thing.

phred

Not yours the car's. Especially now changing seasons, your local refineries could have changed the gas recipe in your area.

This is a known problem with Saabs. Different brands smell different.

Then again, it could be cat time. Don't forget that there should be a Federal emission system warranty and/or a state program. Carefully read the service manual; don't pay for them unless you really have to.

Raoul

Thats the smell. No codes. Is there anyway to have the cat inspected to see if its bad?

Epicman1

It happened to me a several years ago with my 1984 930 Porsche. Turned out that a mouse thought it would be a warm place to spend the night. The car exhaust smelled to high heaven for months.

Suds

Not 100% foolproof but pretty darn good.

A three-way cat (like our cars have) will increase the temperature of the exhaust gases passing through it by at least 30 deg-F. My older Mazda used to show a 50 deg-F difference -- I have never measured my own Audi, though.

You will need to get hold of a non-contact infrared thermometer. The best ones are made by Raytek ($100-$800). 3M makes good ones ($100) or so and I saw one at RadioShack for $50 that might be good enough. It is convenient to get one with laser sighting.

After the engine is thoroughly warmed up (both coolant and oil temps), run the car at 1500-2000 rpm. Measure the inlet and outlet temps of the cat. If the outlet is warmer by a few tens of deg-F, its okay. If the outlet is a few hundred deg-F hotter, the cat is really overheating and will die soon. If the outlet temp is close to the inlet temp, the cat is already dead. If the outlet is cooler than the inlet, the cat is plugged up.

I would be surprised if no codes were set and there was a major problem. As others have pointed out, it might also be due to seasonal changes in fuel or something. And absence of a MIL does not mean there are no codes -- you need to check with VAG-COM to see all the codes.

If you do go the IR-temp route, you can also compare the left and right cat temps. If there is a big difference, that's a definitive sign that one engine bank is not functioning properly. If you can jack up the car or put it on lifts, it will be much easier to measure the temps. Alternately, Midas and smog-test stations will sometimes do the temp-check for you without charge.

I doubt its the fuel pressure regulator -- that can be checked too, but requires a fuel-pressure regulator, adapters etc.

Best of luck and keep us informed!

audifirst

Does it smell like rotten eggs or close to it?
then most likely one or both catalyic converters are shot, best way contact first Audi HQ regards the emissions, they extended the emission warranty coverage.
Call them and ask them, they will tell you to go to nearest Audi dealer, and at dealer they will inspect and test it free of charge and if both or one of them is bad they will replace it under warranty at no cost to you
I have done it on my previous cars without problem..
if they don't cover in your state, best way to test the cat is use hammer and then hit lightly on the side of the cat if you can hear something moving or vibrate inside, then the catalyic converter is shot