White Smoke and Hesitation after Refueling

[trentr98]

So I'm having an interesting problem with my B8 S4. twice now, after I refuel halfway after a low tank of gas, the car has hesitated. the first time it seemed like an hpfp because I got low fuel pressure codes across both banks, but after letting it sit for a few hours it drove fine. This time, I tried starting and the car would start then die immediately. Now, after letting it sit overnight, it'll start just fine, but there's lots of white smoke coming out the exhaust. My hypothesis is that this may be unburned fuel, since it doesn't really smell like coolant and I think it's too much of a coincidence that I'd suddenly have a coolant issue.

Could this be a bad injector? How would you recommend going about diagnosing this? It isn't throwing any codes and runs smoothly just with lots of white smoke.

Thanks!

[carguy19]

You would get misfire codes if you scan the car if it was an injector. You would also smell unburned fuel and feel the cyl not firing (it wouldn't be smooth) and the smoke would be black/dark

Did you scan with OBD11 or VCDS yet?

White smoke is concerning normally and would indicate coolant being burned, could be an intercooler brick leaking, could be a head gasket, could be PCV failure, I would do a proper scan first before everyone goes guessing. How many miles on the car?

[trentr98]

When I scanned it yesterday it had a cylinder 5 misfire and a "hide cylinder" code. It's got ~125k and has had the intercooler bricks and PCV done in the last 20k or so. could the white smoke be excess unburnt gas?

[carguy19]

When I scanned it yesterday it had a cylinder 5 misfire and a "hide cylinder" code. It's got ~125k and has had the intercooler bricks and PCV done in the last 20k or so. could the white smoke be excess unburnt gas?

Fuel makes black smoke, white smoke is coolant or water. So I doubt what youre describing is fuel.

[trentr98]

Thanks carguy, I think I may have wrongly described gray fuel smoke as white condensation/coolant vapor.

Scanning with OBDEleven, there were no codes but I saw that the short term fuel adaptations were ~-7% for both banks. After resetting the short term fuel trims and cycling the car on and off a few times, it’s running perfectly.

Not really sure what keeps causing this type of weird stuff after refueling, but I’m gonna start with replacing the fuel filter and going from there.

Figured I’d provide this update in case anyone runs into these types of issues!