Occasional smell of gas and P0171 code
 

Hey all,

Trying to track down a few seemingly connected issues with our 2017 BRZ.

My GF and I were co-driving at the last autox we did and noticed near the end of the day that the car had a faint fuel smell sitting in grid. It seemed to get stronger over time. We looked all over and could not see any leak inside or outside (track car, gutted interior, easy to see everything). The smell was hard to smell inside the car even with my head inside the back right over the fuel tank, tough to smell from under the car, and only really noticeable at the rear passenger wheel well area. Fuel cap was tight.

At the same time, the car also threw a P0171 code (AFR sensor issue, system too lean). It's worth noting the car was on the fuel light and had very very little fuel in it at the time.

We filled it up and let it sit for a bit during the 2nd run group, then went back and looked it over throughly. Couldn't notice any smell at all.

The smell came back at the end of the hour long drive home. Faint fuel smell that was noticeable in the garage after it had been parked. The code did not return. Since then I've driven it for another 45-50 minutes, didn't notice the smell while driving, but faintly noticed it after driving when it was in the garage. Still no code.

Car is tuned on Ecutek so we were able to datalog... AFRs look completely fine but fuel trims seem a bit off. Seeing about -8 to -10 LTFT. That's the only thing I can see that is possibly off. Can't find any obvious exhaust or vacuum leaks, though I haven't gone too deep into testing for that yet.

Any thoughts?

Wild guess is exhaust leak on your header before the cats

actually that dtc should be triggered by extremely positive fuel trims (more than +35/40%)
exhaust leak could be a thing

also injectors problems
coil pack problems
which means in some cilinders fuel is not arriving/burning therefore ecu tries to add and car becomes richer and triggers dtc

need an extensive log while triggering dtc

Hmm. Unfortunately the code has not come back. I did take extensive logs driving around, but to my untrained eye the only thing I can see that might be out of order is the fuel trims.

Not necessarily convinced that the two events are correlated... but it is interesting it happened at the same time as the gas smell started.

I did check around the exhaust pretty thoroughly from header back. No obvious leaks... nothing I can hear or feel.

I just experienced this on my 2018 BRZ, took it to the dealership and they couldn't find anything. But there wasn't a code. Just a strong smell.



Unburnt fuel smell can make its way out of the engine bay, through the sound tube plug and leak into your cabin.

Could also be a bad fuel mix, or mice damage on one of the lines. I would recommend removing the rear seats and looking around the driver side to check for any mouse droppings.


My last wild guess would be a fuel pump recall that affected the 2018-2019s, there could be a small chance that your 2017 was outfitted with a facelift fuel pump model.

Did you find the smell on yours?

The smell for us is definitely centered around the passenger side wheel well area. No smell at all in the engine bay and you only even smell it inside the car after it's been sitting and the windows are down.

Good to know there's a fuel pump issue on adjacent years... I think I'll pull the access panel to see if everything looks good around there.

I have also been considering that the charcoal canister is around that area, on my STi that needed replacement and it caused a smell. Though the car was 15 years old at the time.

The car is a track car and has a fully stripped interior, doesn't look like anything got in and chewed on anything luckily.