Author Topic: BPY FSI P2177 CEL - Boost leak - Vacuum Leak - Bad Economy Etc (Read 6791 times)

superchicken · « **on:** May 24, 18, 20:18 »

I'm trying to track down a potential boost or vacuum leak.

Engine is a 2007 BPY 2.0T with DSG.

I replaced the intercooler last year with a Golf R unit and greased/checked all the pipes to/from the intercooler then.

Replaced the DV with the upgraded unit then as well.

Car is averaging 11/100 on the highway in cruise at 100-110kph flat roads.

I can hear trumpeting through the CTS intake.

Car throws P2177 code which seems to be a vacuum leak.

Car idles smooth and drives fine, but under part throttle cruise/accel it slowly increases and decreases boost (you can feel a mild surging).

Boost requested / actual seem to be fine.

Anyone know what the diameter of the turbo inlet is so I can make a boost leak test cap? (I'm too lazy to pull it all apart just to measure).

Autohau5 · « **Reply #1 on:** May 24, 18, 20:50 »

What are your fuel trims in 01-08-32-1/2 ? What does a log of MAF (01-08-02-4) look like during a third gear pull from 2000rpm to 5000rpm? Should be a pretty linear increase with very little to no noise.

superchicken · « **Reply #2 on:** May 25, 18, 06:24 »

I'll check those. I'm using obveleven instead of vag-com so I'll have to check what block channel the fuel trims are in.

superchicken · « **Reply #3 on:** May 25, 18, 06:26 »

Group 32

superchicken · « **Reply #4 on:** May 26, 18, 14:32 »

Trims at 110kph cruise flat ish highway - -2.5% and 22.3%

superchicken · « **Reply #5 on:** May 26, 18, 14:35 »

Lambda on a highway pull - -3% and 0.75V

83RedRoc · « **Reply #6 on:** May 27, 18, 09:34 »

group 32 ( or block 32 on VCDS ) is idle long term and partial long term,

So you saying that your partial long term is +22%? If so, it's having to add 22% more fuel on top of base just to try and maintain the requested AFR. These will reset every time you clear DTC's. At 25% I belive that it throws a code.

Could be a bad MAF, and this car is particularly sensitive to intakes, the stock housing isn't round, and the sensor is calibrated specifically for the shape it was from the factory.

superchicken · « **Reply #7 on:** May 27, 18, 17:35 »

Here's a chart of a 4th gear pull. You can see the boost oscillation as well. 80g/s seems way too low for a MAF at nearly full throttle, no?

https://docs.google.com/spreadsheets/d/1sLWWiPelNSWazj2yYmmmuvrIBZPCKjnD5kAskOAh_is/edit?usp=sharing

superchicken · « **Reply #8 on:** May 27, 18, 17:42 »

Boost specified vs. actual

https://docs.google.com/spreadsheets/d/13p8ZuiscR5rF9YJv9aGwd3AYaOGuxqNKwgrZfdPlbbk/edit?usp=sharing

superchicken · « **Reply #9 on:** May 27, 18, 17:49 »

I should mention the boost oscillation existed prior to installing the CTS intake.

83RedRoc · « **Reply #10 on:** May 28, 18, 15:49 »

80g/s is wayyyyy too low. Should be up around 200 if you are on a stock tune. Your MAF is probably pooched.

The logs are weird. I've never seen a request so low, maybe just something to do with it not being VCDS.

superchicken · « **Reply #11 on:** May 28, 18, 17:15 »

Yeah I figured as such, something about being .8 of your BHP in g/s

83RedRoc · « **Reply #12 on:** May 29, 18, 08:29 »

yup. g/s / .8 = rough hp number. This isn't set in stone, but I'm hoping you are making more than 100hp !

But that's why your fuel trim is so far out of whack. MAF see's no air, so if it was controlling it you'd be crazy lean, 02 sensor is adjusting, to compensate but if you are at 25% its reached its maximum value meaning the ecu could still be running a leaner mixture than it wants, it simply has no more room to adjust it.

Autohau5 · « **Reply #13 on:** May 29, 18, 10:03 »

Good sleuthing!!

superchicken · « **Reply #14 on:** May 29, 18, 15:31 »

I'll have to see if anyone in town has a spare mag I can try swapping and I'll clean mine as well. Nic?

superchicken · « **Reply #15 on:** Jun 04, 18, 06:49 »

Cleaned the MAF with a spray and the readings went up to 170-180g/s under full throttle pulls. Wife reports the fuel econ on the last tank was 8L/100km avg.

Autohau5 · « **Reply #16 on:** Jun 04, 18, 07:58 »

Good job. I’ll submit my invoice shortly.

superchicken · « **Reply #17 on:** Jun 04, 18, 21:20 »

Car still surges a bit on boost. Invoice denied!!!

superchicken · « **Reply #18 on:** Jun 14, 18, 21:39 »

I'm back, more charts. The boost oscillation is well defined on partial load acceleration. https://docs.google.com/spreadsheets/d/1ns7YBznbiuxextpEuzhFI_6uaQGpEsP6YVpKvCV15EM/edit?usp=sharing Is the boost spike on initial demand normal for a GTI or should i be looking at my wastegate / N75?

superchicken · « **Reply #19 on:** Jul 18, 18, 22:48 »

superchicken · « **Reply #20 on:** Jul 18, 18, 22:49 »

superchicken · « **Reply #21 on:** Jul 18, 18, 22:49 »

The sawtooth profile on the second chart is what's been driving me crazy.

83RedRoc · « **Reply #22 on:** Jul 20, 18, 09:21 »

your IAT sensor?

superchicken · « **Reply #23 on:** Jul 21, 18, 07:08 »

Pulled the maf and no change in performance, still oscillates. Eventually the car went into reduced performance mode (not necessarily limp). I’m leaning towards DV or wastehate or N75. I should really put it on a dyno.

superchicken · « **Reply #24 on:** Aug 22, 18, 22:26 »

OK, I did a boost leak test this afternoon by hooking up a schraeder valve to the turbo inlet directly and removed the oil cap as to not pressurize the crankcase. I started with 5 PSI, no obvious hissing noises. Upped it to 20 PSI, still no hissing noises. Looks like mechanically the car doesn't have any leaks.

I did hear a gurgling noise coming from inside the valvecover which I suspect would be air pushing past the turbo bearing seals into the return pipe and bubbling back up in the bottom of the pan... but I figure that when the engine has oil pressure those bearings would be sealed up.

So - it's gotta be electrical. I still get an obvious oscillation at part-throttle climbing hills, like the car is rubber-banding, and the fuel economy is terrible. The car makes good power, just drive ability is a bit suspect.

I need to re-log the car to get some fresh data.

Would removing the cat and staying with stock software have an impact? Is the car stuck in cat pre-heat mode?

superchicken · « **Reply #25 on:** Sep 27, 18, 20:00 »

Replaced the D revision DV with the original rubber pierburg unit, (no rips). Doesn't seem to have made a difference aside from now you can hear compressor flutter on throttle lift.

Would a failed N75 be common?

83RedRoc · « **Reply #26 on:** Oct 01, 18, 11:47 »

fairly its just a frequency valve.

If you unplug the rear 02 it won't affect driving, it'll just have a CEL for short to - on the 02.

You can log 118 and see the duty cycle % of the N75.