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High LTFT K04 BPY

ROH ECHT

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The EVAP failures vary from cracks in the canister(not likely) to cracked tubing or a failed purge valve(shown in the first vid). The first vid confirms the issue with the car he has there had a compound issue or more than one problem...and this happens often.

This guy isn't familiar with our 2.0t FSI but he's good at discovering issues. In this, he shows ways to test the common possibilities. He doesn't understand when you clear codes is when you see a jump in the STFT and then it corrects and recalibrates to appear to be fine at idle. You can watch the whole thing which includes smoke testing and a few other checks he performed...or; from about 46 minutes on is a good place to start;

Here's the clear codes and how the idle trims jump and then reset;
 

BurgerGuy

Go Kart Champion
Location
Charlotte
Car(s)
'07 K04 GTI
Thanks for sharing. Would the LPFP seal on the tank be a potential cause for a high positive LTFT? I may need a new locking ring and the gasket was replaced when I put the MK6 pump in Q3 last year. No fuel outside the tank, but when I remove the black cover under the seat I can smell fuel which means it's not air tight.
 

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Possibly, it is the same as a leak in the EVAP system. SO if so, it then has an effect. Smell could be coming from the EVAP canister under the spare wheel unless you are sure the pump seal isn't sealing. The leak detection pump is near there under the fuel filler. How to check it all though? Here's one VW EVAP system description; https://blog.fcpeuro.com/heres-how-a-volkswagen-audi-evap-system-works
 

BurgerGuy

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Location
Charlotte
Car(s)
'07 K04 GTI
It didn't smell like fuel the first time I broke it open. The lock ring has some rust on it (Northern car) so probably a good idea to get a new one. I'll start there and also get a new gas cap. I used a flat head and mallet to tighten the lock ring. What'd you use? Now I wish I knew what my trims were before dropping in the MK6 pump because it would tell me if I didn't properly seal the tank. Will also note that the STFT references I've been making are actually the LTFT (Idle) values. Oops. So really...
  • LTFT (I): +1.21
  • LTFT (P): + 18.35
I'll have to check block 032 to see STFTs. Polar FIS doesn't let you show that data point on the MFD.

Also, for the sending unit on the pump, it can come off. Going to swap it with the sending unit on the other MK5 pump that has the busted return "funnel" if this one is really bad. (y)
 

ROH ECHT

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A 3/4" cold chisel and hammer.

Right, block 1 of MB 032 is LTFT at idle...but MB 033 block 1 is the one that shows what it really is immediately after the codes are cleared...after a bit, MB 032 block 1 adjusts and MB 033 block 1 looks good.

Oh...so you have the original still? Why did you buy the one with the knackered return then? If I may ask?
 
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BurgerGuy

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Location
Charlotte
Car(s)
'07 K04 GTI
It was $40 and I had already put the Quantum pump in it. My guess is the return tube is there to prevent the pump getting hit by pressurized fuel. Could force the electrical connectors off. No bueno. Plus, sending units alone are $100 new and you can't find those used anywhere fast.
 

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I just went out to do the basic setting and looked at the fuel trims after clearing codes. Let it run until the LTFT-idle appeared and it was 0.1%...and MB 033 block 1 was always within 2 to 3%. So definitely no leaks on mine. Have to drive it a bit to determine the LTFT-partial. Remember... ±10% is acceptable.
 
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BurgerGuy

Go Kart Champion
Location
Charlotte
Car(s)
'07 K04 GTI
Well, I probably just eliminated a leak source (see pics). There was oil buildup at the base of the neck. Popped right off with a couple gentle smacks from my mallet. I'll take it for a spin after work and see what the STFT looks like on 033.

I did notice that the car took some time to build up vacuum pressure on initial crank similar to the test that guy ran in his video. I've already ordered a purge valve alongside the gas cap so will swap that when it arrives. After removing the neck, my vacuum is sitting right at 19 Hg instead of just under 20 Hg.
 

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BurgerGuy

Go Kart Champion
Location
Charlotte
Car(s)
'07 K04 GTI
So, trims moving downward. Only to +17.18 on LTFT partial during my short ride yesterday, but once warmed up vacuum sits at about 21 Hg. Before it was just below 20 Hg. The STFT still goes as low as -5 sometimes both at idle and partial. Will see what happens over the next few days.

Would it be better to see how the engine builds vacuum on a cold start or when it's at operating temperature?
 

ROH ECHT

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My first response, to 19 inHg instead of 20 inHg, was it went the wrong way, but then you posted the 21 inHg, LOL.
Did you remove any adhesive left at the new mating surface for the seal of the cap? Mine left a bit although it was a thin layer in spots.Scraping it off while preventing it falling into the engine sucked.

Vacuum building warm or cold; shouldn't matter.

I am still curious of what the short term is right after you clear codes...even if there are no codes. Before starting it, you go to engine-fault codes, and clear codes. Then start it and go right back to measure blocks for fuel trims and look at them...doesn't take long before the short term at idle appears; partial will remain at zero until driven a bit. What are the first trims at idle you see? Or have you done this and the -5% is what you see after clearing codes. I am not sure when you cleared code, but if it has been some time, remember the partial is a long term average. It may be lower than 17%. Clear codes resets the partial and a new average is calculated from driving from this moment on.
 

BurgerGuy

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Location
Charlotte
Car(s)
'07 K04 GTI
Agreed on inHG values. It was still running it's "warm up" cycle when I saw it at 19 inHG, but later that afternoon when I took it for a spin is when I saw it reach 21 inHG. At least I've made another dent. ~1% with the pump and at least 1% or more with the oil cap neck removed. I did try to remove some of the adhesive with a rag, but it doesn't want to budge so I left it. It's not on the inside section of the valve cover anyway. Might try some goof off on a rag and see if that takes it off while the valve cover opening is covered up.

The -5% was showing without clearing the codes and indicated to me it was pulling back on the added fuel, but it didn't stay there. Would fluctuate between +1% and -5%. Even saw it hit -7% a time or two. It needs to be driven for differences to be seen, but I got my first DSG fault code during my ride yesterday for giving it too much gas in 2nd gear. It was..."exciting" and the car is okay. Just can't give it the business in 1st or 2nd anymore. Too risky. Only went about 50% - 60% throttle when it happened.

I can clear codes to reset trim data, but have avoided doing that to see how the system reacts naturally with pre-existing data.
 

ROH ECHT

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Clear codes actually allows you to see the new adjustments quicker in regards to the partial because that is an average on stored data. So it will take longer for the average to come down if fixes you made have a great effect on the trims. It's like fixing something that was causing very poor fuel mileage and not resetting the average mpg on the MFD. You won't see the true mpg it now has due to all the stored mpg before fixing it.
 

ROH ECHT

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That's better. Would've taken a good bit of time to see the new average if not for the clear codes. I still think there's a leak somewhere with the "MB 032 block 1 - 2.2% ltft idle". Curious what MB 033 block 1 did when you cleared codes. Did you see that go up quite a bit and then drop back down as MB 032 block 1 went up to 2.2%? Shows this in the Ross-Tech VCDS vid. I wasn't being very clear in the other posts, but yeah...the vid shows you how to determine if there's a leak. Short term is MB 033 block 1 and is where you look right after you clear codes.

Still a bit lean partial (and idle)...but better than 17.x%.

I'm getting more curious of what its fuel ratio does when you you floor it. Are you not logging the data and only watching it? Lambda should drop but what is it dropping to. Given yours seems lean with the partial...I imagine the lambda isn't dropping as much as it should.
 
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BurgerGuy

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Location
Charlotte
Car(s)
'07 K04 GTI
It pegged to +25% immediately and didn't work it's way down until I started driving. No logs today just watching STFT while LTFT idle and partial adjust. It's up to +11.3 now.

Hesitant to floor it.
 
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