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      12-23-2014, 10:55 PM   #1
mwahlert
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massively positive fuel trims

2008 335i AT
115k miles

for a few months i've been trying to track down the problem i'm having.

car is mechanically stock. cobb OTS tune. (have tried OFT tune as well).

at idle and cruise my LTFTs are massively positive. 20-30%, and often triggering 29E0. fuel trims near 0% under moderate throttle. seem to be the worst at idle.

i had the car at BMW in November, they were unable to immediately diagnose the problem, but were willing to replace the HPFP under warranty as it was the only thing still covered. i paid for them to replace the fuel pressure sending unit (low side) while they were at it.

problem continued and took it to an independent shop last week. they had the intake manifold off while replacing the oil filter housing gaskets and did a walnut blasting. they smoke tested the car and found a small leak in the charge pipe.

i just replaced the charge pipe and still no change in the fuel trims.

any ideas?
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      12-23-2014, 11:12 PM   #2
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I keep getting the 29E0/29E1 codes too. See my thread for everything I've done. Getting ready to replace all of my vacuum lines....

http://www.e90post.com/forums/showthread.php?t=1068200
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      12-24-2014, 12:13 AM   #3
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Quote:
Originally Posted by Wookie420 View Post
I keep getting the 29E0/29E1 codes too. See my thread for everything I've done. Getting ready to replace all of my vacuum lines....

http://www.e90post.com/forums/showthread.php?t=1068200
well, that doesn't sound promising for me...
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      12-24-2014, 12:32 AM   #4
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Originally Posted by mwahlert View Post
well, that doesn't sound promising for me...
When I was getting the lean code mine turned out to be injectors. So if everything else checks out it is most likely your injectors.
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      12-24-2014, 09:35 AM   #5
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I had the same issue a few years ago. Difficult to diagnose. I landed up cleaning my MAP sensor and it solved the issue temporarily. It would suggest doing that first since it's an easy fix. Injectors could be another plausible item. Are you LTFTs off on both banks? If not, then that may help narrow it down to possibly being an injector issue. You could also throw a mild tune on the car and see if you get a misfire, which may also confirm an injector if it's on the same bank as your high LTFT. If both banks are reading high, it's probably some common cause issue. How about your LPFP?
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      12-24-2014, 10:19 AM   #6
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Quote:
Originally Posted by mwahlert View Post
2008 335i AT
115k miles

for a few months i've been trying to track down the problem i'm having.

car is mechanically stock. cobb OTS tune. (have tried OFT tune as well).

at idle and cruise my LTFTs are massively positive. 20-30%, and often triggering 29E0. fuel trims near 0% under moderate throttle. seem to be the worst at idle.

i had the car at BMW in November, they were unable to immediately diagnose the problem, but were willing to replace the HPFP under warranty as it was the only thing still covered. i paid for them to replace the fuel pressure sending unit (low side) while they were at it.

problem continued and took it to an independent shop last week. they had the intake manifold off while replacing the oil filter housing gaskets and did a walnut blasting. they smoke tested the car and found a small leak in the charge pipe.

i just replaced the charge pipe and still no change in the fuel trims.

any ideas?

you should try resetting the adaptations for the O2 sensors, etc. Youll need a bavtech cable or access to INPA to do that, as the cobb version is useless.
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      12-24-2014, 10:25 AM   #7
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Quote:
Originally Posted by mwahlert View Post
2008 335i AT
115k miles

for a few months i've been trying to track down the problem i'm having.

car is mechanically stock. cobb OTS tune. (have tried OFT tune as well).

at idle and cruise my LTFTs are massively positive. 20-30%, and often triggering 29E0. fuel trims near 0% under moderate throttle. seem to be the worst at idle.

i had the car at BMW in November, they were unable to immediately diagnose the problem, but were willing to replace the HPFP under warranty as it was the only thing still covered. i paid for them to replace the fuel pressure sending unit (low side) while they were at it.

problem continued and took it to an independent shop last week. they had the intake manifold off while replacing the oil filter housing gaskets and did a walnut blasting. they smoke tested the car and found a small leak in the charge pipe.

i just replaced the charge pipe and still no change in the fuel trims.

any ideas?
Same issue but my fuel trims are at 18% and been working to try to find the issue for months. The dealer does not have the skill or the tools to helps you. You need to log your LTFT and STFT, Lambda, HPFP, LPFP and battery voltage. Both actual and request. If your fuel trims increase with load and RPM it is going to be a fuel delivery /02 sensor problem. Air leak at the charge pipe will actually give negative fuel trims since your under boost and the leak doesn't have influence on the MAP/TMap sensors. You need to identify if the fuel trim problem are on both banks or just one bank. If your idle vacuum is below -8.5 PSI @ 650 RPM (about 2 degree throttle angle) you have an issue.

Drive the car normally around town and log it over 10 minutes. It is not clear when your fuel trim are positive. It is normal for LTFT to go to 0 at moderate to high throttle input.

1. Do a charge system smoke test to check for leaks at the manifold area and throttle body. Make sure the test was done when they charge the whole system with smoke using the BMW tool. Check for exhaust leak at the manifold and 02 sensors as noted in the BMW doc below.

2. Do a pressure check on the engine and make sure the engine RPM is cycled. it should be about 15-17 mBar idle. If the PCV has failed/ sticking in the valve cover you will know for this test. I would replace the other PCV that goes to the intake anyway. My valve cover PCV was sticking closed and responsible for all my oil leaks.

3. If your fuel trim problem are on both banks it is not the injectors but still possible.

4. If you have an old style LPFP sensor pipe assembly I would replace it out right. This ended up being a problem for me even when the logs said it was working correctly. This part should have been recalled on all pre 09/10 cars as they know it will fail due to vibration.

5. If you pump pressures looks good it doesn't mean much. The pressure can not tell you the fuel volume and there is not way to test this. I would get BMW dealer to do an electrical check on all related components (specificity the LPFP controller). LPFP is number one on my list as a problem but it is a guess. Pumps in series are very difficult to diagnose. In many cases, if one pumps goes they both get destroyed usually by cavitation and not many people know this.

6. Battery voltage should be about 14.5 volts. If it drops below 13.0 volts there might be problem.

7. Check your 02 sensors. I would log voltage. Check if the sensor are tracking well comparing front to rear. Hard to tell a problem with wideband sensors with but amazon sell them for a good price.

8. Check you MAP and TMAP sensors. If they have heavy carbon depots consider replacement.

9. If you can check your C0 and Hydrocarbon and see if they at the high limit for you area this will give you a clue that fuel delivery is a problem.

10. Check for shadow fault codes.

11. An exhaust back pressure test I would do last (checking for clogged cats). The back pressure should be less than 3 PSI for blip throttle test and 0 PSI at 2000 RPM test.

12. Check fuel vapor valve for leaks and function.

I am the point were I just going to replace the whole fuel system out right. No other choice with available data. In my case C0 and Hydrocarbon are way to high but I am lean and have new 02 sensors. It means my fuel pressure looks good but at inject the volume fall short so does the pressure and you get a poor atomization. The faults codes 2fda, 2fca and 2fdb are clear sign of this issue relating to pressure at injection time but can be cam/crank sensors as well.
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Last edited by Orb; 12-24-2014 at 02:10 PM.
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      12-24-2014, 04:10 PM   #8
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to everyone who had this issue: are you guys running a COBB OTS map? i chased the issue for two years until i took the suggestion of one of the members and upped the fuel scalar in the COBB OTS maps. Bumped up the fuel scalar to around 1.1 and all mixture/lean codes have gone away permanently. My fuel economy has gone down slightly so I may have to keep logging and lower the fuel scalar even further (maybe 1.05?) but as of now, no codes, and has been running fine.

BTW, this was after replacing ALL six injectors, spark plugs, all four O2 sensors, endless amounts of resets, intake valve cleaning, and the LPFP (with SteveAZ's 255 inline).
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      12-24-2014, 05:24 PM   #9
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Quote:
Originally Posted by danniexi View Post
to everyone who had this issue: are you guys running a COBB OTS map? i chased the issue for two years until i took the suggestion of one of the members and upped the fuel scalar in the COBB OTS maps. Bumped up the fuel scalar to around 1.1 and all mixture/lean codes have gone away permanently. My fuel economy has gone down slightly so I may have to keep logging and lower the fuel scalar even further (maybe 1.05?) but as of now, no codes, and has been running fine.

BTW, this was after replacing ALL six injectors, spark plugs, all four O2 sensors, endless amounts of resets, intake valve cleaning, and the LPFP (with SteveAZ's 255 inline).
Have not tried that, thanks for the suggestion.
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      12-24-2014, 05:35 PM   #10
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Quote:
Originally Posted by Wookie420 View Post
Have not tried that, thanks for the suggestion.
its gonna take some trail and error, but keep your eyes on those STFT/LTFT. most of these lean codes trigger during cruise: 1500-2500 rpm in 6th gear (around 60-70 mph). I've sometimes seen my fuel trims peg around 20-25% (not good). Use ATR, go to the fuel scalar maps, and change all values (bank 1 and 2) to around 1.05), reload the map, and try again. Adjust the fuel scalar accordingly (higher number = richer, lower number = leaner). You want to see your fuel trims at least under 10%. For reference, the OTS E30 Cobb map has a fuel scalar value of 1.1. Funny enough, I never got these codes when running the OTS E30 maps or my PTF E40 map.
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      12-24-2014, 06:02 PM   #11
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Step 1 with fuel trims that are behaving strangely (assuming you didn't just change mixtures or anything obvious like that) is to reset your adaptations via Bavarian Technic or INPA.

For me, about 9 times out of 10 this has fixed the issue. Same for many others. If nothing else has changed and all of a sudden your fuel trims are out, it's either a learning issue or you have some mechanical problem (or the fuel changed).
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      12-24-2014, 06:27 PM   #12
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Quote:
Originally Posted by danniexi View Post
to everyone who had this issue: are you guys running a COBB OTS map? i chased the issue for two years until i took the suggestion of one of the members and upped the fuel scalar in the COBB OTS maps. Bumped up the fuel scalar to around 1.1 and all mixture/lean codes have gone away permanently. My fuel economy has gone down slightly so I may have to keep logging and lower the fuel scalar even further (maybe 1.05?) but as of now, no codes, and has been running fine.

BTW, this was after replacing ALL six injectors, spark plugs, all four O2 sensors, endless amounts of resets, intake valve cleaning, and the LPFP (with SteveAZ's 255 inline).
my fuel trims are the same w/ OFT stage 1 or Cobb OTS stage 1. Have not verified against stock, yet, as the water pump seems to have taken a dump on me today as well.

i have reset the adaptations many a time over the past few months. this is not a resolution for me.

if the trims are still out of whack on the stock map, it must be a hardware issue.
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      01-02-2016, 08:35 PM   #13
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Same issues here with all of the same replacement parts and numerous adaptation resets via MHD and the JB4. Next is the pre at O2 sensors. Anyone on this thread end up resetting adaptations via INPA and corrected the issue? Why is this different then clearing the adaptations his the tune?
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      03-08-2016, 11:54 AM   #14
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Bringing this up from the dead but I'm seeing the same thing happen, of course I'm running a Cobb OTS tune. I think it is my injectors as I've narrowed the issue down to STFT in bank one being incredibly out to lunch (+25-30%) vs (1-4% on bank 2)
I am curious if resetting everything noted here actually worked?
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      03-08-2016, 02:10 PM   #15
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Since only one bank is lean, you likely have failing injector(s) on the bad bank. Likely have the rough idle at start-up too.
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      03-08-2016, 02:28 PM   #16
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Quote:
Originally Posted by Velocity26 View Post
Since only one bank is lean, you likely have failing injector(s) on the bad bank. Likely have the rough idle at start-up too.
Actually idle is normal at cold startup, it's when she runs for a bit then I'm sitting in traffic where it starts to idle rough. I am thinking I'll need new injectors though.
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      03-08-2016, 04:09 PM   #17
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Quote:
Originally Posted by Velocity26 View Post
Since only one bank is lean, you likely have failing injector(s) on the bad bank. Likely have the rough idle at start-up too.
If trims are positive, correct me if I'm wrong - but that means the DME is adding fuel to compensate a lean condition. If the injectors were leaking, one would expect negative trims.

I don't remember how/if I completely resolved my issue but I started with having a shop smoke test for vacuum leaks as they will cause fuel trims to go positive.
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      03-10-2016, 05:46 PM   #18
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Quote:
Originally Posted by mwahlert View Post
If trims are positive, correct me if I'm wrong - but that means the DME is adding fuel to compensate a lean condition. If the injectors were leaking, one would expect negative trims.

I don't remember how/if I completely resolved my issue but I started with having a shop smoke test for vacuum leaks as they will cause fuel trims to go positive.
Correct positive fuel trims means the DME is adding fuel to compensate for a lean condition. The reason I think that a leaky injector would cause a positive fuel trim instead of a negative one is because the seal on the bottom of the injector would be a little easier to break (less system back pressure) so the fuel pump will have to supply more fuel to the injectors to compensate for the lack of back pressure in the fuel system, hence positive fuel trims.
I've replaced all vacuum lines a couple months ago and had a smoke test performed and I don't have any boost leaks so that can't be the issue.
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      03-10-2016, 06:06 PM   #19
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I had significantly different fuel trims between bank 1 & 2, had a recent valve cleaning, so felt that it had to be injectors. I replaced my injectors with a new set and the trims came back together.

There are several failure modes for an injector, and leaking is only one of them. Sometimes the valve does not have full actuation and is only partially opening, or may be partially clogged. All it takes is one really bad injector to make the entire bank look rich or lean.
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