Your Thoughts On Moderately High Long Term Fuel Trim Adjustments

[old guy]

Lately I have been doing a bit of Interstate driving. I have a 2013 2.0tfsi caeb engine.

While driving, for entertainment I monitor numerous different engine parameters. One thing that I have noticed is that lately while steady state driving my LTFT stays around +4.7%. When I let up on the gas pedal it immediately goes to +5.5% and if I engine brake long enough it climbs to +6.3%. As soon as I resume steady state driving it will immediately drop back to +4.7%. The instantaneous trim acts as expected. Whether at idle, steady state driving or WOT the instantaneous trim stays within a +/- 5% range so that leads me to believe that it isn't a false air condition.

The PCV is fine. I popped the cover off to check the diaphragm and it was intact. Rather than remove the PCV to check the inner flap valve I just replaced the whole thing with the latest OEM AK version. For the record I cannot see any difference at all between the OEM 06H103495J version that I removed and the 06H103495AK version that I replaced it with. The one I removed was perfect. Plugs and air filter were replaced ~2,000 miles ago.

Did a boost pressure test and everything checked out fine. No leaks up to 25 psi. Fuel rail pressure is around 570→580 psi at idle and holds steady around 2,175 psi at full throttle. I ran two treatments of direct inject fuel injector cleaner through the engine.

I have a Neuspeed Power Module installed and I get the same results with it turned off, set at +5 psi or +8 psi. No codes, no misfires, no stumbles at all. Engine runs great! I know that Audi considers anything between +/- 10% normal. However, I'm taking it as a personal challenge to get it down to +/- 2%. It will give me the opportunity to better understand the 2.0TFSI engine. I have a pretty good understanding of the 1.8T engine but I have a lot to learn with the 2.0T.

Thoughts, comments, suggestions are greatly appreciated.

[Spawne32]

thats not high lol the limit for setting a lean or rich code i believe is somewhere between 20-25 + or -, fluctuations between 0-10% are normal from changes in weather/running conditions.

[old guy]

thats not high lol the limit for setting a lean or rich code i believe is somewhere between 20-25 + or -, fluctuations between 0-10% are normal from changes in weather/running conditions.

Yep. I am aware that the limit is +/- 26% and Audi considers +/- 10% normal. I would just like to learn more about how to move the fuel trims one way or the other with the 2.0T. I can adjust the trims on the 1.8T with Unisettings. Unfortunately that doesn't work with the 2.0T.

Other options?

What have you observed with your trims?

[Spawne32]

Yep. I am aware that the limit is +/- 26% and Audi considers +/- 10% normal. I would just like to learn more about how to move the fuel trims one way or the other with the 2.0T. I can adjust the trims on the 1.8T with Unisettings. Unfortunately that doesn't work with the 2.0T.

Other options?

What have you observed with your trims?

ive observed anywhere from 0-6% at any given time, but as far as I am aware, there is no way to change the fuel tables with any sort of high degree of confidence with any of the programs available, even maestro

[old guy]

ive observed anywhere from 0-6% at any given time, but as far as I am aware, there is no way to change the fuel tables with any sort of high degree of confidence with any of the programs available, even maestro

Thanks! I guess I need to find something else to obsess about ;-)

[old guy]

Anyone else care to share their LTFT activity?

[aa2by2]

hello
2010 a5, 2.0 tsfi, ltft at IDLE=13. as load increases it will go down even negative briefly.
research indicates that this is a classic symptom of a vacuum leak.
i have tried to find this leak by trying: applying propane from the throttle body on downstream. also tried spraying wd40. no rpm surges.
there is no great suction when removing the oil filler cap or dipstick, so the pcv diaphragm does not appear to be ripped.

where else might i look for a vacuum leak and what other ways to find it?

car drives and idles fine. no codes. passes emissions.

[flowhigh]

I do the same thing. You also want to look at ST and LT at idle and they'll give you dynamic picture. My long-term does the exact opposite as I read yours. It goes up on throttle and lowers to 6-7 range at idle and - the LTFT. I consider this really good. This is with 75% ethanol content so I don't know if it will relate. A couple of weeks ago I did a carbon treatment and it lowered the number dramatically. There probably a myriad of factors, but one thought is maybe it helped with the desooting the catalytic environment for the O2 sensors.

LTFT just rises as the DI engine age. It's hard to pin it on one thing unless it's in your face. At 4, I don't think you need to even give it a thought. If it's ten or higher consistently then there's something to consider.

Just an anecdotal bit of info: once you clear all DTC's, it also erases your fuel trim settings and it'll take about a week of commuting to fully relearn. I thought it was only a few miles or so.

[old guy]

It was 2.5 years ago when I started this thread and I still monitor multiple engine parameters whenever I am driving. One thing that I have observed is that the brand of fuel I use makes a measurable difference in fuel trims. I always use 93 octane. I generally run down to 1/8 tank before filling up. I have noticed that when I run Shell my LTFT is around +3% to +5% but with Sunoco the LTFT is around +4% to +6% and with BP the LTFT increases to +5% to +7% and as high as +9% at idle. No noticeable difference in performance between the different brands.

I assume the amount of ethanol in the different brands has an effect on the trims.

I'm not sure that I agree with it taking several days for the fuel trims to adjust. I can clear all DTC's while driving and watch the trims adjust back to where they were within no more than 10 minutes of highway driving.

[morris39]

Sorry for stating the obvious. Change in values is the the importrant measurement, not necessarily absolute. Preexisting in accarcies and quirks will be discounted. Of course a baseline and periodic updates are needed. Tracking/monitoring in general does not seem to be discussed much.

[flowhigh]

It was 2.5 years ago when I started this thread and I still monitor multiple engine parameters whenever I am driving. One thing that I have observed is that the brand of fuel I use ...

That was my prior thinking, but I don't know. Maybe it was the treatment that I noticed it took a week for the numbers to subside.

I do notice also the fuel level of all things affects LTFT for some reason. Again, maybe just a CPMA or E85 thing.

[RPMtech147]

From personal experience with these engines and other euro brands, even a pin-hole sized leak anywhere in the PCV or intake system quickly pushes the trims up well into the +20's and pops a lean code right away, especially at idle when vacuum is the highest. If it's under +10% I wouldn't spend any time worrying about it and would only start considering an issue above 15%.