hopkinsd21

Following up here. Well, after lots of homework, these downpipes and cats on the 4.0t do not have flex pipes. So my theory was wrong. I still replaced the downpipes, out of curiosity and wanted high flow cats anyways for the Stage 1 and TCU we just did.

Still getting the fuel smell in the cabin, but once we turn on recirculation, no smell. Nothing has changed except a better and more fun performing vehicle. Gas mileage is better, car runs smoother, no signs of anything major.

Next is following fuel lines from the tank per a previous recommendation.

Mirgy

@Avantily... it was more prevalent with a fuller tank and i could smell the fuel when i stood outside the rear door or opened the rear door to grab a coat or put something onto the rear seat.

My location at the rear of the car when i picked up the smell is what made me suspect the evaporation canister...

With excellent 20/20 hindsight, i now know that when fuel slopped out, during driving, it sat on top of the tank and smelled until it evaporated.

hopkinsd21

Soooo... Seeking thoughts here. Can a faulty O2 sensor, in this case, Bank 1 sensor 1, pre cat, be faulty without a CEL and be the cause of running super rich causing a fuel smell.

My Indy shop says they have never seen anything like this on these types of cars. We did a bunch of work, including high flow downpipes, and was still smelling the fuel smell. They hooked up the computer and was seeing erratic behavior with the air flow. They replaced gaskets as the replacements were much thicker than factory, rechecked everything, still issues. Then we all came to the conclusion to try replacing the O2 as we had no idea is it ever had been replaced. Bank 2 had been replaced last year.

So replace Bank 1 and they covered the Bank 2 under warranty (awesome Indy shop) and now I don't have the fuel smell anymore.

Could a bad O2 be the fuel smell cause?

Avantly

I also smell it with a full fuel tank.

I am in michigan, and a problem we have here is that the sodomite communists have instigated some edict where the previous 10% cap on ethanol content in the fuel is lifted. Audi has a service bulletin out regarding fuel smell on some vehicles when >10% ethanol fuel is used and I am wondering if this is related. There are also TSB's for certain vehicles regarding fuel smell related to leaks from the charcoal canister/EVAP system though I doubt this is the issue as I don't see how a leak back by the canister could make it into the cabin. I will be inspecting my HPFP closely in a month or so and hope to solve this issue, it did first appear during the coronahoax ethanol increases so I still highly suspect it is related to ethanol content.

Dan99

Yes, I had this happen on a new RS5. The fuel pump on my car is located on top of the gas tank, which is under the rear seat. The dealer found that the fuel pump was installed incorrectly at the factory. The gasket was folded in a spot which allowed the leak. It did not show up until about 7000 miles but, I suppose, loosened a bit with driving. They replaced the gasket under warranty. Your leak may be different, but get it fixed.

erik_plus8

Thanks for input. I will investigate my pumps too.

Boostboy

I cannot even believe how much nonsense was said in this thread. Seriously, you guys need to move to Audizine for these types of questions. IDK who that Avantly guy is but he is just yapping. Stop listening to random ppl and start piecing together clues.

First of all, a downpipe, exhaust, any of that would have absolutely nothing to do with any of that. There is a big difference between an exhaust smell ,and a raw unburnt fuel smell.

If you are smelling raw unburnt fuel you have a fuel leak regardless of how you want to look at it. If you are smelling it in the cabin then it is leaking there. If you only smell it in the cabin with your HVAC on, that means its in the engine bay clearly. I also question any of these shops you went to, this is all common sense truly.

And hesitant to rip out your back seat? you literally just pull it up and unplug the connectors. It could not be any easier.

I run full E85 on my car and I do not smell any unburnt fuel. My car absolutely rips and does not skip a beat. Its cringey when people try to politicize things you can tell who is antisocial and sits at home punching air and being mad at the world. its fuel... clean burning cheap race gas, also has NOTHING at all to do with the issue mentioned OR communism. I'm not surprised that guy was banned