Thx guys, I can get those results today. I can see them with OBD Fusion. Should they be read hot?

I've had a BT OBD2 adapter for a few years that I completely forgot I had until I came across it last week and I've had that app for a few years but never needed it for my F30 because I had BimmerCode/Link. Those don't support the E53.

Engine warm for fuel trim and O₂ reading.


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Gotcha.

Do I really need an expensive 10" long swivel 16mm socket for doing the spark plugs?

Nevermind, looked at the prior owner's log and the plugs were at 176Kmi with NGK Iridium BKR6EIX and for some reason replaced again at 187Kmi with Bosch Iridium FGR7DQP+. Shop that did the fuel pump in January recommended replacement but they only have 20Kmi on them so I'm not gonna do that. Also noticed he replaced all the injectors around the same time, VDO parts.

When it comes to plugs i only recall using standard socket/swivel on M54. N55 i needed to get the 12-sided and got the magnet retention model


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OK, got some data.

OBD Fusion only shows 2 O2 sensors. I assume these are the two pre-cats:

Both usually are pretty close to each other, but sensor 1 will drop close to 0 while sensor 2 shows around 0.75 at idle, then rebound. On accel both show around 0.75, and on decel both drop to 0.

Does that point to anything?

upstream sensors will toggle between too high and too low in a square wave if it’s damn stable that’s the downstream sensor or too rich or lean.

now look for the short term and long-term fuel trim


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Dude, what are the fuel trims?

Aha found the trims (not enabled by default)

Short term fuel trim bank 1 sensor 1: 4.7
Short term fuel trim bank 1 sensor 2: 99.2
Short term fuel trim bank 2 sensor 1: 5.5
Short term fuel trim bank 2 sensor 2: 99.2
Long term fuel trim bank 1: –8.6
Long term fuel trim bank 2: –8.6

Hope that is useful.

Yep, heavy negative trim. Car is removing fuel. So certainly not an air leak. This is exactly what I had. I'd swap both those upstream O2 sensors. I'd check fuel pressure and verify you got 50psi. Check and make sure it holds after the car turns off too. Possibly clean the MAF sensor and check your air filter.

Awesome, thx! I’m out all week so I won’t be able to do those things for awhile. I don’t have a fuel pressure gauge but the pump and filter are new. Unsure about the FPR but I have a new Bosch one.


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