[vktr3]

Began watching the ST/LT FT on my '06 325i in an attempt to diagnose ongoing high oil consumption, surging cold starts, and occasional random misfires noticed while stopped at lights.

Fuel trims on 06/08/18 at idle after a 30 minute mixed highway/city drive were:

RPM : 656
STFT 1 : 3.1
STFT 2 : 5.5
LTFT 1 : -3.1
LTFT 2 : -10.2
MAF : .447 lb/min

Notes:
+ while commuting the LTFTs dropped
+ during my morning commute temp was ~ 70° F
+ coolant temp ranged between 200° ~ 212° F (seems a little high but I don't know spec off the top of my head)
+ interesting to note that on my scanner when watching B1S2, B2S2 O2 voltages B2S2 took longer to drop back down after the engine was shut off than B1S2. Could be screen refresh delay or lazy downstream O2 sensor... I wouldn't be surprised as all O2 sensors save 1 upstream are original and should probably be replaced.
+ K&N air filter recently reoiled
+ oil/filter change in april
+ spark plugs changed last year (old ones looked ok upon inspection)
+ engine has 235k miles
+ owned since 2009 with most maintenance done by yours truly

* Early thoughts :
MAF sensor problem, high fuel pressure, leaking fuel pressure regulator, faulty evaporative emissions components, leaking injectors, defective O2 sensors, exhaust leaks/pinholes before the O2 sensor, coolant temp sensor, and base engine issues such as low compression and incorrect camshaft timing.

** UPDATE **
Went out to my trusty ride (second owner since 2009) and took some readings at lunch time (1245). Ambient temp ~80 F, sunny.

On start
STFT 1 : varied between -.8 -> 4.7 until loop closed
STFT 2 : varied between -.8 -> 4.7 until loop closed
LTFT 1 : -4.7
LTFT 2 : started at -10.2 then decreased to -7.8
ETC : 117 F
B1/B2S2 - .425v until loop closed
RPM : ~925 until loop closed (guessing. B1/B2S2 readings were on different screens. will verify this with next test. vibration change from rpm drop seemed to coincide with change in S2 voltage change)

RPMS at ~3k for 1 minute
STFT 1 : .8
STFT 2 : .8
LTFT 1 : -5.5
LTFT 2 : -6.3
ETC : 138 F

Idle post 3k RPM
STFT 1 : 5.5
STFT 2: 5.5
LTFT 1 : -3.9
LTFT 2 : -9.4
ETC : 163 F
B1S2 : .65V
B2S2 : .76V

* NOTE
+ misfire as RPM settled after 3k RPM test
+ attempted supposed throttle body reset (key in, dash lights on from start button push without brake pedal, gas pedal to floor for 5 sec, dash lights out after start button push, release gas pedal)

[W37V]

You say you have high oil consumption... do you have any leaks? These engines are prone to leaks (valve cover, ofh, oil pan). Any mods? What is your oil consumption (quart between oil change?) What’s the mileage on your car? How often do you redline it? What oil are you using (weight)? Did you ever change plugs and coils? How about o2 sensors? Any codes?

[PhaseP]

You have enough difference between bank 1 and bank 2 long term trim levels that, it would be wise first to zoom in on plugs, coils, injectors and maybe 02 sensor. Try to swap them between banks and see if the trim levels follows the swap.

If you have no leaks, the oil consumption could be your oil separator/breather valve and lines to it, especially the return line with check valve integrated into it that goes back to oil pan. Since you have 06 N52 you would have oil separator valve outside of the valve cover.

One other thing that can help is the "rough" INPA screen, which shows all 6 cylinder how they are running from ECU's point of view as the engine is running.

[vktr3]

Originally Posted by W37V

You say you have high oil consumption... do you have any leaks? These engines are prone to leaks (valve cover, ofh, oil pan). Any mods? What is your oil consumption (quart between oil change?) What’s the mileage on your car? How often do you redline it? What oil are you using (weight)? Did you ever change plugs and coils? How about o2 sensors? Any codes?

I'm assuming I have a leak somewhere. Oil consumption is roughly 1L/1k miles. I don't see any obvious leaks on pulley/exhaust sides of the valve cover. Haven't had the belly pan off yet this year but that'll happen when I do both tie rods.

Within the last 2-3 years I've had the OFH and pan gaskets replaced and haven't seen anything that looks like a leak or a seap from those areas.

Car is stock with the exception of the K&N air filter. Hardly redline it. I've been using Castrol Edge/Mobile 1/BMW 5w30 for the life of the car. The plugs were changed last summer around 200k and the coils a few months after.

All O2 sensors have well over 100k on them and I know they should be replaced but haven't gotten to it yet.

Thanks for the feedback W37V!

[vktr3]

Originally Posted by PhaseP

You have enough difference between bank 1 and bank 2 long term trim levels that, it would be wise first to zoom in on plugs, coils, injectors and maybe 02 sensor. Try to swap them between banks and see if the trim levels follows the swap.

If you have no leaks, the oil consumption could be your oil separator/breather valve and lines to it, especially the return line with check valve integrated into it that goes back to oil pan. Since you have 06 N52 you would have oil separator valve outside of the valve cover.

One other thing that can help is the "rough" INPA screen, which shows all 6 cylinder how they are running from ECU's point of view as the engine is running.

Thanks for the swap idea!

Coils/plugs are less than a year old however the injectors are original. I've contemplated pulling the injectors and at the very least replacing the o-rings if not sending them to get cleaned but at the moment I can't really have the car down for more than a weekend until I fix the exhaust on my truck. Not sure if it would make a difference to the injector internals from age but I run Techron every 2-3 months to try and keep them clean.

I have some maintenance that I need to do under the intake manifold (heated angle connector jobby caught fire and torched the leads) so I'll probably replace the CCV (original part) when I do that. Most of the hoses to it are only a few years old but I may have messed up the installation when I replaced them. Forgot about that... Thanks for reminding me!

What sort of things should I be looking for when I look at the rough running screen? I've poked around there before but not really sure what to look for. Most of the green bars look fairly even but I'm not sure if that's to be expected.

Thanks for the reply!

[vktr3]

** Update **

Reset Throttle, Lambda, and VANOS adaptations on Saturday and then went for a nice lengthy drive with plenty highway/back road and city driving. This seems to have had some positive results on the long term fuel trims!

At idle post 30 minute commute

STFT 1 : -1.6
STFT 2: -4.7
LTFT 1 : -3.1
LTFT 2 : -4.7
ETC : 207 F
B1S2 : .76V
B2S2 : .765V

The STFTs seem sort of erratic now. Could be the refresh rate of the scanner but sometimes at a stop light/sign they'll flop around fairly close to 0 but other times they'll stray a bit further from 0.

I'm curious if this adaptation reset will have any long term effect on my fuel efficiency. The majority of my daily commute is highway where I'll cruise between 75-80 mph and get 23.7 mpg reported by the car.

[Noir]

In terms of oil consumption, would definitely consider the ccv valve...
My car was drinking the oil.
At least I learned suuuuper short trips are not good for that particular piece.

[vktr3]

I've noticed over the last few days that when coasting the STFT for both banks sit at zero. This seems counter-intuitive to me in that typically when coasting a RPMs are typically well above idle. Today I noticed (and in the past too) that after my 30+ minute commute home, when idling in the parking lot, the STFT for both banks were bouncing around -10%. I've read a lot about what negative LTFTs mean but not STFTs. Looks like it's time for more research.

[PhaseP]

While coasting and engine RPM is above 1K rpm no fuel is injected to burn. Basically watching how the mpg needle behaves on my car, if gas pedal is not depressed and engine RPM is above 1K, no fuel is injected. If gas pedal is not depressed and engine RPM goes below 1K, computer starts injecting just enough fuel to eventually stabilize idle RPM at 650.
Of course if gas pedal is depresses regardless of RPM fuel is injected in proportion to the gas pedal.
So, your values while coasting maybe because of this; if no fuel is being injected, there is nothing to compensate the fuel amount delivered.

[vktr3]

Thanks for all of your insight! Really helped me think through a few things! LT Fuel trims are still varying depending on the weather and time of day but not over -10 like they were. Max either will seem to hit is ~-7.5.

Still need to hunt the random misfire issue. Usually happens after a 20+ minute high speed (80 mph) trip once I come to the first light. I'm leaning toward leaky injectors or failing FPR because of the often erratic and/or hard (possible starter related as it's the original unit) starts.

[Michaelwaito]

Im still scratching my head as to why some people dont have fuel pump problems while others do. I had one as well. Shouldnt it be more widespread?