M54B30 lean condition

[pickle_party_247]

Hello all, been chasing a lean condition since I bought this car last September (2003 3.0i roadster). For further context these codes were thrown up during motorway/a road driving only, not on start up/ during low speed driving.

P0171 = Fuel Trim, Bank1 System Too Lean
P0174 = Fuel Trim, Bank2 System Too Lean

Dealership replaced all sparks & coils free of charge, I found that the lower intake elbow was pretty torn so had them send me a new one under warranty and installed it myself- car was still throwing lean codes after this.
Specialist suggested CCV and related hose replacement- still hasn't fixed this although it was needed given the state of it!
Next suggestion was exhaust lambda sensors that weren't reading properly- didn't resolve the codes. Smoke test carried out on the same day didn't reveal any intake system leaks.

In the last few hundred miles since the lambda sensor replacement I've noticed strong fuel smells when starting and turning off the car and increased fuel consumption when the engine hasn't warmed up compared to previously- could it be faulty injectors/fuel pump causing this engine code after all?

 

[bigwinn]

Hi mate

I had a running issue which I used inpa to look at the injector performance

I replaced 4 and 5 this week and it’s solved it

If you are near to me in Lincs feel free to drop over?

Cheers

Stuart

 

[pickle_party_247]

Hi mate

I had a running issue which I used inpa to look at the injector performance

I replaced 4 and 5 this week and it’s solved it

If you are near to me in Lincs feel free to drop over?

Cheers

Stuart

Would love to take you up on that but I'm based down in Hants- I will be up that way the last weekend of next month though if the offer still stands!

 

[bigwinn]

Totally! Drop me a pm and we can sort something out

 

[colb]

Air leaks are usually the cause of lean codes and the smell of fuel could be overfueling. Since you have smoke tested the system that would seem to rule out the air leaks as a cause. No mention of your Maf being looked at, that could be a cause if its not reporting correct amount of air passing through it. Take a look at how its performing in live data.

 

[pickle_party_247]

Air leaks are usually the cause of lean codes and the smell of fuel could be overfueling. Since you have smoke tested the system that would seem to rule out the air leaks as a cause. No mention of your Maf being looked at, that could be a cause if its not reporting correct amount of air passing through it. Take a look at how its performing in live data.

when I had a look at the live data this morning the MAF was reporting a flow of roughly 3.5g of air/second at idle- is that typical?

 

[colb]

Not sure about your reading would have to compare with a like engine to see what that idles at. However you should be able to see its performance using INPA or other software/Scanner to see if its registering with movement of the throttle pedal as the revs increase. My experience with Mafs is that they don't always set codes if faulty but can upset the other sensors downstream of the Maf which of course will mess up fuel trims as the car tries to compensate. Have you looked at fuel trims in live data to see if they are showing high, that would explain overfueling as it tries to compensate for what the exhaust sensors are picking up as a lean mixture.
https://www.youtube.com/watch?v=5JaPksGMAy0
Update
Just found this thread on Bimmerfest, good read for testing Maf's
https://www.bimmerfest.com/threads/testing-mass-air-sensor.441285/

 

[spazmochad]

Whereabouts in Hampshire are you?

 

[BumpyZ4]

I had lean codes on mine that drove me nuts and end the end it turned out to be a bad gas from a gas station. New gas and the lean codes went away.

 

[pickle_party_247]

Whereabouts in Hampshire are you?

Up near Alton mate!

 

[pickle_party_247]

Not sure about your reading would have to compare with a like engine to see what that idles at. However you should be able to see its performance using INPA or other software/Scanner to see if its registering with movement of the throttle pedal as the revs increase.

Yep, can see the MAF readings increase as I give it more throttle. I had given the MAF a careful clean with MAF cleaner spray when I was investigating this last autumn/winter so I had kind of ruled it out as the cause.

Have you looked at fuel trims in live data to see if they are showing high, that would explain overfueling as it tries to compensate for what the exhaust sensors are picking up as a lean mixture.

STFTs are showing at around 4-5% on bank 1 and 6-7% on bank 2, LTFTs are 26.56% on bank 1 and 24.22% on bank 2 which seem high from reading other threads on the matter- apparently LTFTs should read between 10-12% from what I read.

If it's not the MAF and not the intake (although smoke tests aren't perfect so specialist could have missed something) then what else could it be? Faulty DME?

 

[enuff_zed]

A few posts back bigwinn mentioned injectors.
Don't think you answered as to whether those had been changed or not?

 

[pickle_party_247]

A few posts back bigwinn mentioned injectors.
Don't think you answered as to whether those had been changed or not?

Nothing's been done to the injectors on the car, I was asking if faulty injectors could be causing the lean condition codes

 

[enuff_zed]

A few posts back bigwinn mentioned injectors.
Don't think you answered as to whether those had been changed or not?

Nothing's been done to the injectors on the car, I was asking if faulty injectors could be causing the lean condition codes

Well Stuart kind of suggested that, so maybe that's the next step?

 

[colb]

STFTs are showing at around 4-5% on bank 1 and 6-7% on bank 2, LTFTs are 26.56% on bank 1 and 24.22% on bank 2 which seem high from reading other threads on the matter- apparently LTFTs should read between 10-12% from what I read.

Yes the LTFT's look on the high side to me, have you tried resetting the adaptions so it learns the fuel trims from scratch?
If you are confident the Maf is reporting ok then injectors would be the next thing to check out. You could pour in a bottle of injector cleaner and run the car to see if that makes any difference to the fuel trims.

 

[pickle_party_247]

Took a new set of readings today and looked at them in some more detail- oxygen sensor 2 on bank 1 seems to be malfunctioning, it has much higher voltage readings than the other 3 sensors and does not report an individual short term fuel trim % unlike the other sensors.

O2 sensor 2 (bank 1) voltage vs O2 sensor 2 (bank 1) STFT%



For comparison:

O2 sensor 2 (bank 1) voltage vs O2 sensor 1 (bank 1) voltage



O2 sensor 2 (bank 1) STFT% vs O2 sensor 1 (bank 1) STFT%



Seems like a likely culprit...anyone know how to get at this sensor for replacement plus part no.?

 

[colb]

Had a quick look at Realoem site E85 3.0i 2006 build date here https://www.realoem.com/bmw/enUS/showparts?id=BT52-EUR-06-2004-E85-BMW-Z4_30i&diagId=18_0497

Your pictures in your post are not displaying.

When viewing live Lambda data in graph form the pre cat sensors should when engine warmed up be showing a regular wave form as their voltages range up and down. The post cat sensors dont usually move much unless there is something wrong with what they are seeing, mine look pretty static.
Could be you are onto the root cause of your troubles with any luck.

 

[pickle_party_247]

Had a quick look at Realoem site E85 3.0i 2006 build date here https://www.realoem.com/bmw/enUS/showparts?id=BT52-EUR-06-2004-E85-BMW-Z4_30i&diagId=18_0497

Thanks for the link, looks like the ticket!

Your pictures in your post are not displaying.
When viewing live Lambda data in graph form the pre cat sensors should when engine warmed up be showing a regular wave form as their voltages range up and down. The post cat sensors dont usually move much unless there is something wrong with what they are seeing, mine look pretty static.
Could be you are onto the root cause of your troubles with any luck.

Image links above fixed- for context this data was recorded with a fully warmed up engine- I'd pulled over to check the sensor readings on my way home after a motorway run. Sensor 2's waveform is nowhere near as responsive or regular as Sensor 1 so definitely seems suspect!

 

[axelleveau]

Image links above fixed- for context this data was recorded with a fully warmed up engine- I'd pulled over to check the sensor readings on my way home after a motorway run. Sensor 2's waveform is nowhere near as responsive or regular as Sensor 1 so definitely seems suspect!

I would not compare the sensor 1 and 2 from the same bank as they are indeed supposed to be different. Sensor 1 which is pre-cat is cycling up and down because the engine hovers around stoichiometric ratio to get the cat working. The Sensor 2 which is post cat is then supposed to see a steadier voltage. I expect this is also why it does not have trims as sensor 2 is mainly (only?) here to check the cat works properly while sensor 1 is used to trim fuel (correct injectors, make sur we get the proper fueling, etc). I feel like your sensor 2 reading is bad though, I would expect a much steadier reading about 0.7V

 

[pickle_party_247]

I would not compare the sensor 1 and 2 from the same bank as they are indeed supposed to be different. Sensor 1 which is pre-cat is cycling up and down because the engine hovers around stoichiometric ratio to get the cat working. The Sensor 2 which is post cat is then supposed to see a steadier voltage. I expect this is also why it does not have trims as sensor 2 is mainly (only?) here to check the cat works properly while sensor 1 is used to trim fuel (correct injectors, make sur we get the proper fueling, etc). I feel like your sensor 2 reading is bad though, I would expect a much steadier reading about 0.7V

Yep it looks bad compared to Sensor 2 on bank 2 as well. Disappointing as these were replaced in February with new parts :|



I'm going to rule out the injectors as the cause of the fuel trim issues before having the sensor replaced though.