Appears to me the lambda is goosed but just to get a 2nd opinion:

 

Actual Voltage- didn't take the right screen shot- swings upto 0.9, slowly comes back down to near 0, stays there, slowly comes back up with hardly any oscillation

 

 

AFR- with a couple of pedal blips to check levels- always lean and VERY lean being reported as soon as the throttle is pressed

 

Which lambda probe is this ? Pre cat should sweep, post cat should be even (ie not sweeping)

Bank 1 sensor 1 so pre cat

Got any logged with VCDS in the excel format ??

 

 

I can get a better grasp with those and make pretty graphs !!

Most cars I've worked on the pre cat sensor should sweep from 0.5v to 4.5v ie it should always be above 4.5 or below 0.5. The way I used to test them was get the car warm so it's off open loop( cold start ) then hold the revs at 2500rpm for 1 min the drop to idle and observe the readings. I may be wrong with the vag stuff but that's how we used to test the jap stuff.

I'm graphing in real time on Torque Pro for the lambda. Checking every last thing I can think of for this weird problem, going to go and check them again in a bit as I've been working the actuator in case that's been a touch sticky on the wastegate. Pain waiting for temps to heat for lambda but ah well, needs must .

Most cars I've worked on the pre cat sensor should sweep from 0.5v to 4.5v ie it should always be above 4.5 or below 0.5. The way I used to test them was get the car warm so it's off open loop( cold start ) then hold the revs at 2500rpm for 1 min the drop to idle and observe the readings. I may be wrong with the vag stuff but that's how we used to test the jap stuff.

Aye, I've been having a search for what the range was on these and drew a bit of blank but the curve shape is normally a dead giveaway with them...ho hum, off out again

If it's leaning it could be a fuel delivery issue, Pump, filter, injectors or FPR 

 

 

 

Have you replaced anything so far ??

Blank off that pipe and then see how it drives

That was already done this morning Clive and was the same.

Right, worked the wastegate by hand disconnected from the n75 for a good 10 minutes and now the pin and wastegate hinge are cop slipped up. Took it out and kicked it Tits properly for 20 minutes - high revs, lots of heat and the more logs of the afr and actual bank 1 sensor 1 voltages and bingo. Seems OK (crosses fingers).

Dave, it was a boost issue and been trying to nail it down as it was a chicken and egg thing. Alternator did not feel like it was sticking when I tried it before, nor did it this time but working it for 10 mins seems to have freed something

The boost can be cut by the ecu under allsorts of conditions as a fail safe, so what appears to be a boost leak is infact nothing of the sort.

 

 

Smoke test is the only way to be 100% on the leak front.

 

I've been here myself, and fuel pump fixed the boost drop. 

Quite a bit of info in this thread http://www.briskoda.net/forums/topic/267641-the-18t-diag-thread/

 

 

How are your fuel trims looking ??

Here's the AFR afterwards dropping down to rich after you take your foot off the throttle as it should and not going upto 25 (damn!) when you press it.

 

And the Lambda- cycling up and down as it should...WEIRD

 

It was only happening when hot Dave thus I thought Lambda or possibly the heat changing resistivity of the N75 and stopping it working correctly. INstead it appears the heat was sticking the wastegate- TBH I'm still not 100% sure if it was the actuator and wastegate but it's running fine for now

Edited 26 February, 201412 yr by Nerd

Just a note to add from my fiddlings Torque ain't the best for numbers it can be a bit out 

On things like AFR it's spot on, same with voltages, only thing it ever goes mad on is boost tbh. With this (lambda especially) it wasn't specific voltages I was looking at, more the shape of it cycling back and forth with in a range which it is now. And AFR should always go a bit rich when you let off the throttle whereas it was doing the total opposite before- regardless of the absolute figures if you get me

The AFR still isn't rock steady at idle which is probably the injectors being a bit dirty but just running some injector cleaner right now which help a bit with that. And short term trims were never more than 3% either way when absolutely nutting it around my 'test' roads which is fine really and long term was 0-1.5% when I was checking which again is fine in my book.

 

Torque is never the best of things but it wins for me because I have it running on my phone mounted to the dash so I can be logging and looking at live values as I drive with worrying about a laptop getting a bit damaged when it's just me doing it. VCDS does certain things better (like n75 cycles for example) but sometimes all you need are the rough and ready values you get out of torque pro

Edited 26 February, 201412 yr by Nerd