[designatedposter]

i've got a pretty high positive fuel trim (lean condition) on my m235i.
i am running bm3, but i flashed back to stock and the positive fuel trim persists.
long term fuel trim (LTFT) is about 1.15 when on part throttle.
no problems at idle.

recent modification includes upgraded silicone turbo inlet.
car is at ~70k miles, had the valve cover gasket replaced recently by dealer by warranty (reused valve cover)

i'm thinking the problem is any of the below:
1. pre cat o2 sensor malfunction
2. intake leak at the crankcase vent line (connects valve cover to turbo inlet)
3. intake leak at the turbo inlet connection to the new pipe
4. the new inlet causes the fuel trim issue (assuming no leaks)

what you guys think

[thejeremyman9]

Post the logs. IF you had a vacuum leak you would probably get a MAF or air-mass related code too. You need to look at both LTFTs and STFTs really. You can try unplugging the MAF to see if it makes a difference, IIRC that basically "disables" the LTFTs.

[designatedposter]

https://www.bootmod3.net/log?id=62f0...0b432dfabc4ff9

Sure I can disconnect MAF, but if that disables ltft, then are you suggesting relying on stft data to determine if there is still a fuel trim problem at all

[BMWILUVU]

1.15 is high?

[designatedposter]

Disconnected MAF.
Ltft is about 0.97
Stft fluctuates within 10 percent , looking normal.
https://www.bootmod3.net/log?id=62f1...729b2acbc96feb

I guess I'll clean the MAF and reconnect.

[designatedposter]

Originally Posted by BMWILUVU

1.15 is high?

You tell me! What's your ltft and where you located and what fuel do you use

[thejeremyman9]

You can try cleaning the MAF as a first step. Are you running an intake? Also what makes you think you actually have a lean condition? Just because you have high LTFTs doesnt mean the car is running lean. Infact in the first log it looks like your STFTs are actually fighting the LTFTs, so the LTFTs are dumping excess fuel and the STFTs are trying to correct that by pulling the fuel back out. So, something is causing the abnormally high LTFTs. Could be an intake, MAF issue, etc. And yes, i would consider 1.15 high, thats 15% fuel correction

[n55david]

Originally Posted by thejeremyman9

You can try cleaning the MAF as a first step. Are you running an intake? Also what makes you think you actually have a lean condition? Just because you have high LTFTs doesnt mean the car is running lean. Infact in the first log it looks like your STFTs are actually fighting the LTFTs, so the LTFTs are dumping excess fuel and the STFTs are trying to correct that by pulling the fuel back out. So, something is causing the abnormally high LTFTs. Could be an intake, MAF issue, etc. And yes, i would consider 1.15 high, thats 15% fuel correction

The 02s will show if it is lean.. fuel trims are just a correction factor as you know..

OP needs to post a log at idle after it warmed up, a cruise log and a wot log.

[thejeremyman9]

Originally Posted by n55david

The 02s will show if it is lean.. fuel trims are just a correction factor as you know..

OP needs to post a log at idle after it warmed up, a cruise log and a wot log.

I know, i think he assumed that, because LTFTs were positive, the car was running lean. But it actually looks like the LTFTs were making the car run rich, then the STFTs were correcting by pulling fuel back out. A WOT log would be much easier to "read"

[n55david]

Originally Posted by thejeremyman9

I know, i think he assumed that, because LTFTs were positive, the car was running lean. But it actually looks like the LTFTs were making the car run rich, then the STFTs were correcting by pulling fuel back out. A WOT log would be much easier to "read"

Oh yeah, in that case I totally agree.
I think you were correct about cleaning the maf etc.

I did a full adaptions reset the other day after fixing my charge pipe issue and I was showing 1.25 on my stft was funny at wot. Much better now.

[designatedposter]

Cleaning MAF did not help, nor does resetting adaptations since that happens automatically whenever a new tune is flashed and I've bounced between stage 2+ and stock. Both have high ltft.

I mentioned running lean simply as a reference to the car needing to actively add fuel in the manner of positive long term fuel trim. I know that the ltft is preventing car from actually running lean.

My intake is stock filter and I modified the stock box by cutting out the lower portion similar to the mppk.

I refrained from putting a wot log because I am running wmi and that would add confusion since my stft will be removing fuel.

At idle, both ltft and stft are 1,no issues.

At highway cruising, 65mph, that where you'll see ltft creep up to 1.18 and stft will stay +/- 5 percent.

Here's a wot log
https://www.bootmod3.net/log?id=62ef...729b2d5d520323

[thejeremyman9]

Originally Posted by designatedposter

Cleaning MAF did not help, nor does resetting adaptations since that happens automatically whenever a new tune is flashed and I've bounced between stage 2+ and stock. Both have high ltft.

I mentioned running lean simply as a reference to the car needing to actively add fuel in the manner of positive long term fuel trim. I know that the ltft is preventing car from actually running lean.

My intake is stock filter and I modified the stock box by cutting out the lower portion similar to the mppk.

I refrained from putting a wot log because I am running wmi and that would add confusion since my stft will be removing fuel.

At idle, both ltft and stft are 1,no issues.

At highway cruising, 65mph, that where you'll see ltft creep up to 1.18 and stft will stay +/- 5 percent.

Here's a wot log
https://www.bootmod3.net/log?id=62ef...729b2d5d520323

Sounds like a hardware issue. The bolded part above - (not critiquing what you said btw just observations) but based on what i am seeing in the logs the car doesnt actually need the fuel, its adding fuel when it doesnt need it, then its just pulling it back out with STFTs. Did you change anything right before this happened?

There was one other guy on here who had a similar problem and tryed basically everything. His was worse though, his LTFTs were getting extremely high like +25%, to the point where the car was throwing rich code IIRC. I dont think he ever found the problem.

If you reset adaptations is it temporarily better until LTFTs are relearned? Or is it immediately like this again the first time you go for a drive?

The positive LTFTs indicate the car is consistently seeing more air than is metered by the MAF, so its adding more fuel that would be calculated by just relying on the MAF values alone. So, could be a vacuum leak after the MAF.

Youre right about the WOT log, doesnt help since you are running meth on OTS map.

[designatedposter]

i don't think the STFT is compensating for the LTFT. you can see here that LTFT=1.18 and STFT=1 https://www.bootmod3.net/log?id=62f1...729b2acbc97015

LTFT fuel trim only gets enabled seemingly after driving a few miles after a tune is flashed.

as for recent modifications, yes, the silicone turbo inlet, which is why i suspected a vacuum leak between the MAF and turbo. potentially in the crankcase vent hose that is pretty easy to break during the install (and not visible because it is wrapped in insulation).

ultimately, i think the LTFT is the result of MAF readings vs the o2 sensor. if the MAF sensor reads 'x' amount of air, then 'y' amount extra gets drawn in after the MAF, then the o2 reading would be off, thus driving the DME to add fuel via the LTFT.

when i disconnected the MAF, the DME relies solely on the MAP, which eliminates the variable of the vacuum leak pre turbo, and all is seeming well.

[thejeremyman9]

Originally Posted by designatedposter

i don't think the STFT is compensating for the LTFT. you can see here that LTFT=1.18 and STFT=1 https://www.bootmod3.net/log?id=62f1...729b2acbc97015

LTFT fuel trim only gets enabled seemingly after driving a few miles after a tune is flashed.

as for recent modifications, yes, the silicone turbo inlet, which is why i suspected a vacuum leak between the MAF and turbo. potentially in the crankcase vent hose that is pretty easy to break during the install (and not visible because it is wrapped in insulation).

ultimately, i think the LTFT is the result of MAF readings vs the o2 sensor. if the MAF sensor reads 'x' amount of air, then 'y' amount extra gets drawn in after the MAF, then the o2 reading would be off, thus driving the DME to add fuel via the LTFT.

when i disconnected the MAF, the DME relies solely on the MAP, which eliminates the variable of the vacuum leak pre turbo, and all is seeming well.

I see that in that log, yes. The other one looks like STFT was as negative as the LTFT was positive.

Gotcha, i would agree with that assessment. I replaced the CCV hose when i installed my inlet, i could hear it cracking when i removed it. 50k miles is about its life anyways, if you touch it at all.

Assuming your CTS fit snugly into the turbo (metal piece with o rings into turbo), and then the silicone was tight onto that piece, and intake tight into CTS silicone at the top side, those shouldnt be leak prone. All those connections were very tight for me. That really just leaves the CCV hose. I would just replace that.

[n55david]

Originally Posted by thejeremyman9

I see that in that log, yes. The other one looks like STFT was as negative as the LTFT was positive.

Gotcha, i would agree with that assessment. I replaced the CCV hose when i installed my inlet, i could hear it cracking when i removed it. 50k miles is about its life anyways, if you touch it at all.

Assuming your CTS fit snugly into the turbo (metal piece with o rings into turbo), and then the silicone was tight onto that piece, and intake tight into CTS silicone at the top side, those shouldnt be leak prone. All those connections were very tight for me. That really just leaves the CCV hose. I would just replace that.

I can attest to the cts inlet being very tight on the turbo fit for sure lol. It was easier to install the pure short one that you have to cut the stock inlet up.

[designatedposter]

Originally Posted by n55david

I can attest to the cts inlet being very tight on the turbo fit for sure lol. It was easier to install the pure short one that you have to cut the stock inlet up.

How's your cts inlet for clearance from the head? Mine rubs and I notice some wear on the inlet. Hopefully it doesn't rub through in a year

I ordered a new ccv hose and I hope I can replace without removing the inlet again, that was a pain of a job.

[n55david]

Originally Posted by designatedposter

How's your cts inlet for clearance from the head? Mine rubs and I notice some wear on the inlet. Hopefully it doesn't rub through in a year

I ordered a new ccv hose and I hope I can replace without removing the inlet again, that was a pain of a job.

I hadn't noticed anything. I'll take a look at it tomorrow.

[designatedposter]

new ccv hose and no change.. a new MAF is approx $180 and im hesitant to waste that money since my logs show no issues on the MAF. i tried cleaning using the special solvent spray, no luck.

i'll have to make a local friend who will loan me his MAF for testing.

[AmuroRay]

Originally Posted by designatedposter

new ccv hose and no change.. a new MAF is approx $180 and im hesitant to waste that money since my logs show no issues on the MAF. i tried cleaning using the special solvent spray, no luck.

i'll have to make a local friend who will loan me his MAF for testing.

car-part.com

https://www.car-part.com/cgi-bin/sea...ey=&userPage=4 $ 50 bucks or so

[designatedposter]

update: problem still exists. check out some logs:
1. no load, idle, 2000rpm, 3000rpm.
https://www.bootmod3.net/log?id=63ee...729b648a9a4707
2. transition from MAP vacuum to MAP pressure (gas pedal and brake at same time)
https://www.bootmod3.net/log?id=63e7...90c62cebd78e3a

what's been done so far:
-PCV vent hose (between valve cover and turbo inlet)
-primary o2 sensor
-smoke tested (low pressure) from turbo inlet
-intake manifold gaskets
-filled engine bay with smoke while idling and did not notice any vacuum leaks (though it'd be hard to see)

suspect list:
-cat to turbo gasket (i've removed and replaced cat several times all on same gaskets)
-MAF (though it seems to be working just fine, and no difference when i unplug it)
-PCV valve / diaphragm (though i tested it and seems to hold pressure from the external nipple just fine)
-valvetronic seal?
-vanos solenoid/seals??
-injectors??
-cracked intake manifold??

[harkes]

Originally Posted by designatedposter

update: problem still exists. check out some logs:
1. no load, idle, 2000rpm, 3000rpm.
https://www.bootmod3.net/log?id=63ee...729b648a9a4707
2. transition from MAP vacuum to MAP pressure (gas pedal and brake at same time)
https://www.bootmod3.net/log?id=63e7...90c62cebd78e3a

what's been done so far:
-PCV vent hose (between valve cover and turbo inlet)
-primary o2 sensor
-smoke tested (low pressure) from turbo inlet
-intake manifold gaskets
-filled engine bay with smoke while idling and did not notice any vacuum leaks (though it'd be hard to see)

suspect list:
-cat to turbo gasket (i've removed and replaced cat several times all on same gaskets)
-MAF (though it seems to be working just fine, and no difference when i unplug it)
-PCV valve / diaphragm (though i tested it and seems to hold pressure from the external nipple just fine)
-valvetronic seal?
-vanos solenoid/seals??
-injectors??
-cracked intake manifold??

Just checked the idle log... I am not super familiar with BM3 lingo but I dont really see any problems. LTFT at 1.1 and STFT pulling it down slightly to idle a tiny bit lean at ~14.9. My PWG idles at 14.7 - not sure if EWG are exactly the same

[designatedposter]

ltft 1.1 means +10% fuel is being added to reach target afr. When cruising on highway it can get up to ltft 1.25. the problem is that when I go heavy on throttle, the 'problem' disappears but since the ltft is so far positive that the stft has to correct by going negative. This is okay until I hit the limits of the stft which is 30% then the afr cannot stay on target.