Audi A4 quatro 1997 2.8 12v
I just scanned the engine with VAG-COM 409.1:

VAG-COM Version: Release 409.1-US
Chassis Type: 8D - Audi A4 B5
Scan: 01,02,03,08,15,17,25,35,45,55,56
-------------------------------------------------------------------------------
Address 01: Engine
Controller: 8D0 906 266 B
Component: 2,8l V6/2V MPI OBD2 D02
Coding: 01201
Shop #: WSC 20205
2 Faults Found:
16538 - Oxygen (Lambda) Sensor B2 S1: No Activity
P0154 - 92-00 - Unknown Error Elaboration
17514 - Shareware Version. To Decode all DTCs
P1106 - 92-00 - Please Register/Activate
(17514 P1106 O2 Sensor Circuit (B2-S1) Voltage Too Low - Air Leak A - that's after a search on the net for that code number)
Readiness: N/A
-------------------------------------------------------------------------------
Address 03: ABS Brakes
Controller: 4D0 907 379 L
Component: ABS/EDS BOSCH 5 4171
Coding: 0265109043
Shop #: BB 34171
No fault code found.

Is that a problem related just to the oxygen sensor or might be something else as well? Could that cause the hard start and the fuel smelling oil?

Here are my previous post about the same problem:

I just joined this forum after buying an Audi that I cannot yet enjoy...
Audi A4 1997 2.8.
The oil smells like gas, there was also quite a bit of sludge on the engine cap. The car seems to run good but ocassionally (1 of 10) it is very hard to start. It cranks but does not turn over. Starts after several attempts and looks like it helps when pumping on the accelerator while trying to start it up. Plus I have to wait for about several minutes between the attempts. In those cases, when I start it up, it dies easily the first few minutes .
When I don't have problem starting it (9 of 10 times) it does not hesitate and does not die.
All filters, ignition wire set, spark plugs and the fuel pump relay were changed but it did not help...
Any help would be highly appreciated.

Unfortunately things are getting even worse. I got the engine cleaned/flushed with BG "Quick Clean" and then changed the oil. The previous oil was not too bad, but it smelled like fuel.
I put 1 pint of Seafoam in the gas tank and filled it up.
Then I drove the car for about 20 miles. The new oil also definately smelled like fuel although it stayed at the same level on the dipstick and still slick and nice, so I guess not that much fuel got into it. It was clean and nice on the dipstick but there was coarse sludge on the crankcase walls and on the crankcase cap. There was a thin finer layer of buildup on the shaft too. Is there a way to get rid of all that sludge in the engine at once?
Later in the evening, after a hard start and a little cranking, I drove for about 10 miles and "Check Engine" light came on.
After driving the car for a while - since I bought it - I also noticed a grinding noize while stepping slightly on the gas - most noticable on lower gear and lower rpms. At higher rpms and highway speed the noize disappears. Looks like it is coming from the front, perhaps a little on the right side.

 

O2 sensor and a hard start concern? ABSOLUTELY! Get that sensor changed, they rear O2 sensor won't cause any starting problems but the before cat O2 sensor measures everything on how the engine is running for fueling and how much air is being passed through so the answer is yes.
Replace the B2 S1 sensor, driver's side before cat O2 sensor, replace that and clear the fault codes, that should take car of all your problems.

 

THANKS A LOT!!!! Sounds optimistic! I guess that the 2 oxygen sensors are different - is there a model # or something, so I make sure that I buy the right one. Is it hard to be replaced?

 

They aren't too hard to replace, any they do have different part numbers from side to side. Go to ECS tuning, they have em for about $120 and make sure you get the right side (bank 2 or drivers side)
To replace it just remove all the plastic engine covers, cut the zip ties holding the O2 sensor harness in place set it aside and reach down behind the engine and you will be able to feel the sensor. You will need an O2 sensor wrench or socket to break it loose.

 

THANK YOU SO MUCH FOR ALL YOUR HELP!!!!
Just one more question (for now ) - did you see the fault code:
17514 P1106 O2 Sensor Circuit (B2-S1) Voltage Too Low - Air Leak A
Could that 'Air Leak' mean and vacuum lines on top of the O2 sensor or this is a result of the faulty O2 sensor?

 

Probably a result of the O2 sensor, if there was a vaccum leak there would be a lean fault code for both banks. The O2 sensor can mask a lot of problems as well as create others, so replacing that sensor should be the first thing on your list to do.

 

during start up the 02 sensors are in open loop meaning they dont read at all and the ecm is in default(meaning thatit would not be related to a hard start) Now if you had a bad enough vac leak you could set a fault for 02s just like I have seen throttle valve faults set for a vacuum leaks. Not to say that the 02 isnt bad but check the easy first. I would say that auditech is incorrect in the fact that an 02 will cause a hard start. you can disconnect your 02 and the car will still start but try disconnecting the vacuum line from the brake booster and see how easy it is to start. There are not many vacuum lines on a 2.8 tho like there is on a 1.8

 

^^^^^^Its not the fact that the O2 is in open loop rather that the ecm has learned what the O2 sensor is reading that makes the car hard to start. After replacing the sensor it takes the ecm some drving time and lots of starts to get the ecm to re-adapt after the fault codes have been cleared.

 

how many miles on the car. you may have bad rings causing hard starts, fuel in the oil and if oil is getting by the rings and into the exhaust it could foul out 02 sensors. I still do not agree that an 02 will cause a hard start. the 02 does not even come into play when starting the car

 

110 000 miles. Bad rings is very bad and expensive, isn't it?