High LTFT K04 BPY

[BurgerGuy]

Much to check;
Dipstick o-ring replaced
EVAP tubing this would be the line runnning from the rear of the car to the back of the valve cover, through it, and out the front, right?
Brake Booster and tubing just replaced the tubing, but not the booster. Smoke test will show if it's the problem.
Vacuum lines
Intake connections including the MAF to intake seal all tight.
Boost to throttle body connections if you're referring to the charge pipe that connects to the throttle body then it's tight.
Intake manifold for cracks is there a common failure point on these?
Do you notice oil seepage anywhere? Seal those connections or replace damaged tubing VW tech said there was some on the belly pan, but not sure where it's coming from.
Have it smoke or pressure tested if all else fails to find it. once DSG is in I'll be doing this.

It is possible it is only a leak...but I think yours may also be poor fuel delivery by injectors or the MAF.
Reading this helps explain how a leak usually doesn't affect "partial/off idle" as it does at idle and stft. http://wiki.ross-tech.com/wiki/index.php/Fuel_Trim_Info

The injectors are OEM new. So is the MAF. Both replaced this year.

Based on your partial and idle comment it sounds like I have both then. STFT shoots to +25% after clearing codes and the LTFT partial is high. It doesn't fluctuate as much anymore. Hanging between +13.28 and low +14.

See above in red.

I'll also add that removing the leaking oil cap neck from the valve cover brought the LTFT partial down by 5-6%. Makes me wonder if the channels inside the cover are falling apart too like yours did. If I smoke tested through the rear breather tube or evap port and saw smoke coming out of the oil fill on the valve cover that would indicate there's a problem, right?

 

[ROH ECHT]

Yes...it would show from the filler if tested in that way. I imagine the EVAP in back would be best/easiest due to its size.

I can only see it affecting the trims if the EVAP route were not sealed...because if the PCV were not, the air is already metered at the MAF.

 

[BurgerGuy]

Got the car back. Replacement DSG is so quiet/smooth. Shop found another vacuum leak at the hose connecting to the brake booster.

LTFT idle now -0.56. Partial +12. Decent improvement.

 

[ROH ECHT]

Nice on the DSG. And the leaks? They just seem to keep coming don't they? Not all of it may be leak related...fueling parts and their performance can affect ltft as well.
I need to look at the new data on mine now. I know there are no leaks but the fueling is all new. I last saw ltft partial at 6 or 7%. I need to look at the lpfp "target and actual" anyway, so I will have a look at the new stft and ltft as well. My mpg has gone up drastically. Its average was 23.0 to 23.5 mpg (it was a task trying to keep it above 23 mpg) prior to replacing the fueling bits and now is 29.0 mpg.

 

[BurgerGuy]

Mine's around 25-26mpg right now. Up from 19-21mpg. Feels more composed, but still room for improvement.

Went for another drive and partial trimmed up to +14, idle at -0.56 just about always.

 

[ROH ECHT]

What's frustrating with yours is you keep finding one leak after another and still the LTFT remains.
I would seriously consider smoke testing the intake, vacuum, and evap systems. But again, it could be filthy injector nozzles or something else causing the O2 to report a lean lambda to the ECU.

 

[BurgerGuy]

I doubt it's dirty injectors. They're less than 6 months old. Will smoke test soon. At least I'm getting closer.

 

[BurgerGuy]

Well, I've finally got the car back. Swapped in a new to me DSG with 54k miles on it only to find out the clutch seal had a small leak. Went back to the shop to get that fixed and also had them install a LSD. The shop found a vacuum leak on the hose connecting to the brake booster so fixing that along with the front hose got my idle trims in check which are now floating between -0.9 and +0.5, but off idle (P) is still sitting high at ~+16. I'll bring it in for a smoke test to see if I can find another leak source, but I gotta say...it's finally a blast to drive. Fuel economy and power are up. Engine/exhaust noise down slightly. Engine is the smoothest it has been since I got the car.

I've also...

• Reverted to OEM PCV setup with updated valved rear breather
• Replaced cam follower
• Installed new rev D DV without DV+ because I think it closes too fast for my setup.
• Installed new Sachs flywheel

 

[ROH ECHT]

So when you clear codes and start it...the LTFT at idle is no longer jumping up?
If you have leaks all sorted, and there's a +16% LTFT partial and good injectors, it could be low pressure fueling or incorrect reporting of the MAF or a Temp sensor(air or coolant).

 

[BurgerGuy]

Right after clearing codes it usually goes up to about +1, then settles down to -0.9 over time. Minor fluctuations from there. Partial starts out at zero, then slowly climbs to ~+16.

I'm still running that Quantum pump, but may go back to the MK6 GTI pump. I've noticed when the car gets down to a quarter tank I sometimes get a mild fuel cut while light on the throttle. LPFP DC spikes to 90%+, then settles back down. The MAF is new as of this year so I doubt that's it. I also replaced the temp sensor on the intake manifold earlier this year, but could do the one for coolant as well for safe measure.

This the coolant temp sensor you're referring to? 06A919501A

 

[ROH ECHT]

Yeah, unfortunately mine would only run well with the Quantum under light load...under heavy throttle it just had nothing.

Yeah, I believe that is the number. There are two yes? One is for gauge and fan. So if the gauge reading looks normal, it may be the other to replace. One by the thermostat and the other near the rear of engine. I just do not know which does what.

I still have to wonder if the positive LTFT is the tune and are others tuned by the same having the same fuel trims. Otherwise, this could be a wild goose chase of replacing more parts. Mine is at +7% right now. I think of the slim possibilities; I believe the MAF is accurate-it's data shows it to be, O2 is not long ago replaced, PCV is good, new injectors-LPFP-fuel sensors and all, no data deficiencies other than +7%. Not really much help as no one wants a list of $#!@t to replace...I know I hate these sorts of issues.

I think it can only be a leak when there is an addition to LTFT partial and you are running in vacuum. If the LTFT partial changes to rich when in boost...this would mean it has a leak. Which I doubt since its LTFT now looks to be solid. But you could try that to confirm it leaks or not. This would at least point to the thing is simply reporting it is running lean when off-idle and in vacuum.

 

[BurgerGuy]

Yeah, unfortunately mine would only run well with the Quantum under light load...under heavy throttle it just had nothing.

Yeah, I believe that is the number. There are two yes? One is for gauge and fan. So if the gauge reading looks normal, it may be the other to replace. One by the thermostat and the other near the rear of engine. I just do not know which does what.

I still have to wonder if the positive LTFT is the tune and are others tuned by the same having the same fuel trims. Otherwise, this could be a wild goose chase of replacing more parts. Mine is at +7% right now. I think of the slim possibilities; I believe the MAF is accurate-it's data shows it to be, O2 is not long ago replaced, PCV is good, new injectors-LPFP-fuel sensors and all, no data deficiencies other than +7%. Not really much help as no one wants a list of $#!@t to replace...I know I hate these sorts of issues.

I think it can only be a leak when there is an addition to LTFT partial and you are running in vacuum. If the LTFT partial changes to rich when in boost...this would mean it has a leak. Which I doubt since its LTFT now looks to be solid. But you could try that to confirm it leaks or not. This would at least point to the thing is simply reporting it is running lean when off-idle and in vacuum.

Did you mean idle where I changed to red?

I've not yet replaced my O2 sensors nor have I ruled out any leaks inside the valve cover or EVAP system.

When I asked Unitronic what kind of trims I should expect to see they only said "what's your goal?" ...lol. They may not be willing to divulge such information, but I'll give them a call and see if they're willing to shed more light.

 

[ROH ECHT]

No...partial is off idle or multiplicative.

I've not yet replaced my O2 sensors nor have I ruled out any leaks inside the valve cover or EVAP system.

Good.

"What's your goal?"

...LOL. I would've replied "What's your goal?"

You should try seeing what the lambda is while driving at different rpms. Hold the rpm steady (and at varying rpms) and note what Stoich is being reported...have someone else take note if you feel the need. If your fuel is 10% ethanol...Stoich should be 14.05.

Do you have a Catalyst on the DP? Have you checked the injectors for leaks with VCDS? I know...leaking injector? But if one leaks it reduces pressure to the others.

 

[BurgerGuy]

I can view lambda from the MFD so will see what it does next time I'm out and about. And yea, 14.05 would translate to about .98 - .99 when viewing data from the ECM, correct? 1 would be 14.7

Am running a high flow cat. Have not checked injectors. Is that a visual inspection or something I need to log to see? I can monitor rail pressure, LPFP pressure, controller duty cycle, and other stuff right from the MFD, but I know logging is more revealing as it shows the data at x load and x rpm.

 

[ROH ECHT]

Checking the injectors for leaks would be done when it has been running and is at normal op temps. Then you shut if off and watch the high pressure actual. As you probably know, the rail pressure increases from heat as it sits there after shut-off. You just watch the actual rail pressure as it rises. Does it reach the FPRV limit or does it not? My FPRV is a 145 bar limit and will bleed off at about 155 bar. Stock FPRV might bleed at 130bar and the RS4 at about 135 or 140 bar...can't remember what people have said. So if you see pressure rising after shut-off but not reaching the limit...then it is leaking from an injector or the FPRV itself leaks. Yes...you could just log the rail pressure data, but this isn't as reliable as the HPFP is under working mode to reach and maintain the target pressure and a leak may not show in the data. You might as well watch the low pressure at the same time to see if it holds the low pressure while shutdown.

Oh, and yes on the lambda. It will be difficult to tell if it shows lean because it is making the fuel trim adjustment. But see if it reports higher at a few different rpms. Try at a constant; 1500, then 2500, and finally at 3500. Does it seem to report higher than 14.05/14.7=95% at any of those rpms? I am seeing the 10% ethanol value being said to be from 14.05 to 14.13...so, over 96% is what I would look for. This may work more accurately if you clear codes to reset the LTFT. But I truly do not know if this really gives you a true reading because of it needing time to calculate the fuel needed to add all over again. But worth a shot.