Troubleshooting Intermittent Fuel Smell

[drivem3]

Recently, after a round of maintenance my E46 has been having intermittent fuel smell in the cabin. It mostly occurs while stopped in traffic/at a light or after a hard pull. The issue came about after replacing the following items:

• Spark plugs
• Injectors
• Precat O2 sensors
• Fuel filter

Initially, the smell was worse and I took it back to a shop to diagnose where they found the fuel trim to be high and the reset adaptations after the O2 sensor replacement. I was also having issues with low speed sputtering and they found that the aftermarket K&N filter was causing issues so I have since replaced that back to stock.

Has anyone run into similar issues? Shop thinks that it could be using Bosch O2 sensors instead of genuine OEM sensors. Before spending >$1200 on OEM sensors trying to see if it could be something else causing the issue. Currently no CEL on and car is running strong.

[Slideways]

Does it smell like raw fuel? That would point to a leak at the fuel filter or at the injector rail.

Rich, unburnt exhaust could be a defective O2 sensor. Genuine BMW sensors are made by Bosch.

[karter16]

OP - if its a raw fuel smell and you get under the car to check the fuel filter it would also be worth checking the push-fit hard-line connections about halfway to the back of the car. They're easy to knock when you're under there and can appear as though they're clicked in properly, but actually aren't quite.

[BL92]

Same as mine, Fuel filter was leaking, just nip it up and was all good

[bigjae46]

Quite possible they pinched an o-ring when reinstalling the injectors or the cross-threaded the regulator body onto the filter.

Geez, they blame the air filter? lololol...might be time to find a new shop. Nay....definitely time to find a new shop.

[drivem3]

Does it smell like raw fuel? That would point to a leak at the fuel filter or at the injector rail.

Rich, unburnt exhaust could be a defective O2 sensor. Genuine BMW sensors are made by Bosch.

How would I pinpoint if it is actually a defective sensor? Would that throw any codes?

[drivem3]

OP - if its a raw fuel smell and you get under the car to check the fuel filter it would also be worth checking the push-fit hard-line connections about halfway to the back of the car. They're easy to knock when you're under there and can appear as though they're clicked in properly, but actually aren't quite.

That was my thought as well, but I brought it back to them and they checked underneath (and sent video) and doesn't appear to be any leaks. When you say check the hard-line connections halfway to the back of the car, do you mean the ones that not right next to the fuel filter?

[drivem3]

Quite possible they pinched an o-ring when reinstalling the injectors or the cross-threaded the regulator body onto the filter.

Geez, they blame the air filter? lololol...might be time to find a new shop. Nay....definitely time to find a new shop.

Pinching the o-ring on the injectors would cause this too? How would I know which injector, would removing and reinstalling the same injector relieve the pinched ring?

[Slideways]

How would I pinpoint if it is actually a defective sensor? Would that throw any codes?

Usually, it would.

My guess is there is a leak in the fuel system.

[bigjae46]

Pinching the o-ring on the injectors would cause this too? How would I know which injector, would removing and reinstalling the same injector relieve the pinched ring?

Yes, would cause a fuel leak. Then it would come into the cabin through the cabin filter.

Once the o-ring is pinched it goes in the trash. You probably can just pop the hood watch the injector rail and have someone rev it.

[drivem3]

Yes, would cause a fuel leak. Then it would come into the cabin through the cabin filter.

Once the o-ring is pinched it goes in the trash. You probably can just pop the hood watch the injector rail and have someone rev it.

Actually I misstyped, the injectors were not touched. It was the ignition coils, would ignition coils/spark plugs cause any fuel smell if they were faulty?