Chasing lean codes

[BMWM3186]

Have tried various things to fix lean codes. Seems more lean at idle running about a 10% long term and 8% on the highway. Smoke tested and found the small vacuum plug at the back of the intake manifold leaking. Didn't help fuel trims at all but it did help some of the rough cold starts. Codes only come on after a hard pull up to about 70mph and then letting off according to the freeze frame.

I tried cleaning the maf thinking that the new oiled air filter I put in may have gooped it up but still no luck.

Next step is to pull the disa whenever I'm back home and check it.

Any other ideas or suggestions? I'm running out

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[GotZHP]

Do you have lean codes for both banks?

+10 % isn't too bad, but ideally it'll be a single digit number. When I had my vacuum leaks I was in the +15-25%.

If you have codes for both banks and you are positive you do not have any vacuum leaks, maybe fuel delivery? Any auto part store will loan you the gauge to test your fuel pressure and it is super easy to do. Just pop the engine cover off and connect to the Shrader valve.

That's where i'd start since it is free.

[BMWM3186]

Do you have lean codes for both banks?

+10 % isn't too bad, but ideally it'll be a single digit number. When I had my vacuum leaks I was in the +15-25%.

If you have codes for both banks and you are positive you do not have any vacuum leaks, maybe fuel delivery? Any auto part store will loan you the gauge to test your fuel pressure and it is super easy to do. Just pop the engine cover off and connect to the Shrader valve.

That's where i'd start since it is free.

lean codes only on one bank but the fuel trims are about the same on both. The short term fuel trim was at 8% and the long was at 8% (so 16% total) when it tripped. assumed it couldn't be a fuel problem since the lean conditions happen with less load. I did have a vacuum leak that I found with my cigar smoker but to my surprise didn't really change fuel trims at all...

[GotZHP]

Did you use a siphon pump to go with the cigar or were you just using the good old lungs? If you were just using the ol' iron lung, I'd recommend doing another smoke test like in the video below. You get much more flow of much thicker smoke! I burned a cigar down in about 30 seconds and found 3 leaks last week.


https://www.youtube.com/watch?v=rYna4mTVZCE

The guy is annoying but that is the tool you need. I got Pennzoil siphon pump at home depot for $10. Can use it for other tasks around the house / car as well.

https://www.homedepot.com/p/Pennzoil-9-62-in-Multi-Use-Hand-Pump-36677/205092031


How many miles are on your car?

[BMWM3186]

Did you use a siphon pump to go with the cigar or were you just using the good old lungs? If you were just using the ol' iron lung, I'd recommend doing another smoke test like in the video below. You get much more flow of much thicker smoke! I burned a cigar down in about 30 seconds and found 3 leaks last week.


https://www.youtube.com/watch?v=rYna4mTVZCE

The guy is annoying but that is the tool you need. I got Pennzoil siphon pump at home depot for $10. Can use it for other tasks around the house / car as well.

https://www.homedepot.com/p/Pennzoil-9-62-in-Multi-Use-Hand-Pump-36677/205092031


How many miles are on your car?I was using a transfer pump on the cigar. Pumped enough into the intake to almost get the glove to explode on the intake from the pressure. 104k miles

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[GotZHP]

I'd say try cleaning the DISA and the ICV valve next but if those were stuck wouldn't the car run rich at idle?

Could just be age on the MAF or another one of the electrical components. I'll go take a data log of my car today to see what I get for trims now that my vacuum leak is gone, but I know I need an O2 sensor, so the data may not be the most reliable.

Do you still have original O2 sensors? And original MAF and DISA?

[BMWM3186]

I'd say try cleaning the DISA and the ICV valve next but if those were stuck wouldn't the car run rich at idle?

Could just be age on the MAF or another one of the electrical components. I'll go take a data log of my car today to see what I get for trims now that my vacuum leak is gone, but I know I need an O2 sensor, so the data may not be the most reliable.

Do you still have original O2 sensors? And original MAF and DISA?Yes, all of that is original.

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[GotZHP]

If your positive its not fuel related then maybe you have an O2 sensor that is on the way out? Do you have the ability to log them? Since we have similar fuel trims after fixing vacuum leaks that would be my next guess. I had been logging about the same for fuel trims and was watching my O2 sensors as well and sure enough one was lazy. It didn't throw a code until just the other day.


Without logging for data, its a shot in the dark. I bought a Bluetooth to OBDII adapter and an app to go with it for about $40. Def worth the investment!

[BMWM3186]

If your positive its not fuel related then maybe you have an O2 sensor that is on the way out? Do you have the ability to log them? Since we have similar fuel trims after fixing vacuum leaks that would be my next guess. I had been logging about the same for fuel trims and was watching my O2 sensors as well and sure enough one was lazy. It didn't throw a code until just the other day.


Without logging for data, its a shot in the dark. I bought a Bluetooth to OBDII adapter and an app to go with it for about $40. Def worth the investment!Yeah thanks. I just ordered a Bluetooth adapter so I can use the app on my phone again because I lost my other one. I'll check more things when I get home in a couple weeks. My friend has got some fancy snap on tools and diagnostic data so hopefully we can figure out more then.

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[GotZHP]

I'd recommend OBDLink MX device with OBDFusion App. Torque works too but I've heard it has more bugs