2001.5 Audi S4 Limpmode with no CEL

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LimpMode

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Slight Background:
Was told turbos were failing and that they would die soon and that is why my CEL was on and the car didn't feel like it had the right power. Fast forward to now, 4 yrs later.. replaced turbos myself to find that the old turbos were being held on with half-of-one bolt on both sides (so basically the car was all motor for the last 4 years, I guess those piggy pipe weren't as loud as i though they were...) a list of recent repairs and mods are below. Car is now running, better than it has in years, smooth and feels good, no CEL, but feels under-powered. Will randomly "wake-up" where it pulls like a freight train and then goes back to what I believe is limp mode.

Took some logs (links below) and I notice that I never really get more than 1450mbar (which to my understanding is really just 450bmar after accounting for atmospheric pressure). Which puts me at 6.5psi
Its driving me nuts that I can't figure out whats going on with this car, there are no CEL, I preformed the readiness procedure passed everything, gas consumption is a little heavy in my opinion but I have been doing quite a lot of WOT logging so I can't tell if that is a symptom or not, as far as I can tell she is running really well but not boosting as she should be. As of right now I have no idea what I should look into next or try to do to diagnosis it further. I may try and make a smoke machine and try to do another boostleak test this weekend.. I really hope someone on here has some insight.

Not proficient with VAG-COM logging yet in how all the values work together so please excuse any ignorance on my part, please set me straight... I'm here to learn.
Also maybe worth mentioning: Was a high altitude car (Denver CO) and I now live at sea level. Not sure if that will mess with the tune but I thought I'd say it just in case.

List of Mods:
EPL Stage 1 tune (bought with car, never confirmed other than a reputable shop in CO telling me that it is in-fact a stage 1 tune)
2.0t coil conversion with ICM delete
Piggy pipes
XS power SMIC with silicon fittings <--probably going to go back to stock in a month or so as fitment is something left to be desired
Upgraded mounts all the way around
Single mass flywheel conversion

List of recent repairs:
Head Gaskets (and all the things that go with it, i.e valve cover gaskets, cam seals, etc)
replacement K03s with new CHRAs and hardware
Timing belt & waterpump
OEM RH Boost lines
New Clutch
Both Sensor 1 (upstream) Oxygen sensors

Diagnosis in order performed:
boost leak test - None found
MAF O-ring missing -replaced
Brake booster grommet deteriorated- replaced
Swapped MAF and MAP with known working car- No Change in performance, logs are essentially the same

AutoScan: https://drive.google.com/open?id=19QKJO8MgEoBEO4ecI2QBmUOEgFHbCB_Y

Vag-Com Logs (4runs): https://drive.google.com/open?id=1N6M7yfHejjLKgKgiNZw6a2OtroZTgMgk

Readiness log: https://drive.google.com/open?id=1e9w3UrOg4rbCWbdFFb6oLz6_krA2_lt6
 
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Uwe

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   #3  

LimpMode

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These links all produce 404 errors. Please post your data in-line. It's just text. Copy & paste it.

-Uwe-
I repaired all the links.

Here is everything other than the logs. that looked way to funky to post on here, but like i said the link is repaired

AutoScan:

Code:
Monday,02,September,2019,15:27:20:17986
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 7 x64
VCDS Version: 19.6.1.0 (x64)
Data version: 20190529 DS308.0
[url]www.Ross-Tech.com[/url]


Mileage: 304961_2   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Chassis Type: 8D - Audi A4/S4/RS4 B5 (1995 > 2002)
Scan: 01 02 03 08 15 16 17 25 35 37 45 55 56 57 67 75 76 77
 
-------------------------------------------------------------------------------
Address 01: Engine        Labels: 078-907-551-AZA.lbl
   Part No: 8D0 907 551 M
   Component: 2.7l V6/5VT     G   0002  
   Coding: 06711
   Shop #: WSC 63351  
   VCID: 34691A2F047D2DEF4D-515A

No fault code found.
Readiness: 0110 0100

-------------------------------------------------------------------------------
Address 03: ABS Brakes        Labels: 8D0-907-389.lbl
   Part No: 8D0 907 389 E
   Component: ABS/ESP allrad      D56  
   Coding: 04395
   Shop #: WSC 06435  
   VCID: 356F272B0F0734E77A-515A

No fault code found.

-------------------------------------------------------------------------------
Address 08: Auto HVAC        Labels: 8D0-820-043-1D.lbl
   Part No: 8D0 820 043 P
   Component: A4     KLIMAAUTOMAT D58  
   Coding: 00160
   Shop #: WSC 63351  
   VCID: 2D5F0F4BE7577C2702-259E

3 Faults Found:
00779 - Outside Air Temp Sensor (G17) 
            30-00 - Open or Short to Plus
00792 - A/C Pressure Switch (F129) 
            31-00 - Open or Short to Ground
01206 - Signal for Duration of Ignition Off Time 
            27-10 - Implausible Signal - Intermittent

-------------------------------------------------------------------------------
Address 15: Airbags        Labels: 8D0-959-655-AI8.lbl
   Part No: 8D0 959 655 G
   Component: Airbag Front+Kopf  1002  
   Coding: 00304
   Shop #: WSC 63351  
   VCID: 3A7534172619DB9F97-51B2

1 Fault Found:
65535 - Internal Control Module Memory Error 
            00-10 - - - Intermittent

-------------------------------------------------------------------------------
Address 17: Instruments        Labels: 8D0-920-xxx-17.lbl
   Part No: 8D0 920 981 B
   Component: B5-KOMBIINSTR. VDO D12   
   Coding: 02264
   Shop #: WSC 22098  
   VCID: 2B5B0153D94372171C-515A

No fault code found.

-------------------------------------------------------------------------------
Address 35: Centr. Locks        Labels:. 8D0-862-257.clb
   Part No: 8L0 862 257 N
   Component: CV-Pump             D11  
   Coding: 16172
   Shop #: WSC 06325  
   VCID: 408146FF40C5814FD9-4F02

No fault code found.

-------------------------------------------------------------------------------
Address 45: Inter. Monitor        Labels: 4B0-951-173.lbl
   Part No: 4B0 951 173 
   Component: Innenraumueberw.    D03  
   Coding: 00101
   Shop #: WSC 22569  
   VCID: 60C1A67FE005E14FF9-4B32

No fault code found.

-------------------------------------------------------------------------------
Address 55: Headlight Range        Labels: 4B0-907-357-AUT.lbl
   Part No: 4B0 907 357 
   Component: LEUCHTWEITEREGLER  D004  
   Coding: 00012
   Shop #: WSC 63351  
   VCID: 65CFB76BFF2784670A-51D0

No fault code found.

End-------------------------(Elapsed Time: 03:43)--------------------------


Readiness:

Code:
Monday,02,September,2019,17:15:53:17986
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 7 x64
VCDS Version: 19.6.1.0 (x64)
Data version: 20190529 DS308.0
[url]www.Ross-Tech.com[/url]


Mileage: 304961_readiness   Repair Order: 



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


Readiness Status: 0000 0000
Exhaust Gas Recirculation: Passed
Oxygen Sensor Heating: Passed
Oxygen Sensor(s): Passed
Air Conditioning: Passed
Secondary Air Injection: Passed
Evaporative Emissions: Passed
Catalyst Heating: Passed
Catalytic Converter(s): Passed
 
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Uwe

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Actual manifold pressure seems to follow specified fairly well. But specified strikes me as quite low for a tuned car. Is it possible this tune has some kind of "switch" to put it in "stock mode"?

-Uwe-
 
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LimpMode

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Would this be normal for a stock car? It seems that the boost is low for even that..

As far as a switch goes there is none that I'm aware of. I'm really considering trying to source another ECU and see if that's the issue. I cant think of anything else other then maybe the check valves? I figure anything else would cause a trouble code if it was acting up.

It's just so strange that the car randomly surges with power and then settles down again. Is it possible the ECU bricked itself because of the constant out of whack parameters over the years? Is there any way to check that?

Is there anything else I should log to help try to narrow this down?
 
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Uwe

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I never had a B5 S4, but IIRC, they used relatively mild amounts of boost in stock form; not much more than half a bar, and your logs show the ECU requesting half a bar.

-Uwe-
 
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Samz09

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Id consider 2 things, Because the car ran like crap for so long the computer adapted to its self. So first thing i would do is clear out the stored memory by doing a capacitor discharge. Basically take the 2 battery terminals off the battery and hold them together for a minute to drain any stored voltage and wipe out adaption values. Then connect them and go for a test drive, half boost, and full send.

If that solves it all the way cool, if mostly fixed, id look into changing the N75 valve. they can act up and not give codes.

For a smoke test, id use a professional machine, if you dont have it then atleast bring it to a shop just for that to confirm no leaks, a lot of weird things can happen with a 2.7. One instance was the passenger wastegate vacuum line. Oem is a hardline with a crimp, then the rubber line is 1 inch long, with the heat wrap around it, ive seen that tiny hose with a tear in it. If you "made" a machine and didnt find anything. Let a shop just do that part.
 
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Uwe

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Id consider 2 things, Because the car ran like crap for so long the computer adapted to its self. So first thing i would do is clear out the stored memory by doing a capacitor discharge.
That really shouldn't be necessary for an ECU. Clearing fault codes alone resets any limp mode it might be in, as well as the fuel trims. One could also do a reset in Adaptation Channel 0.

-Uwe-
 
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Samz09

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That really shouldn't be necessary for an ECU. Clearing fault codes alone resets any limp mode it might be in, as well as the fuel trims. One could also do a reset in Adaptation Channel 0.

-Uwe-
I havent used that method. I suggested that because i had a car, 2.8 passat v6 that had been driven with clogged secondary cats for so long, untill it wouldnt move. After gutting them ( it literally looked like melted lava rock inside, The car had misfires on one bank that wouldnt go away. After checking everything possible with clearing codes, 3 times and nothing. Held the terminals together for a minute. Started the car and it was flawless :banghead:
 
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LimpMode

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Thanks for all the input guys.
I tried connecting the terminals and it didn't get me anywhere, it was worth a shot. I've been reading up on the N75 valve and it from what I read my problem is very similar, I'm going to use the one out of my friends car later today and see it that fixes it. I'll report back either way
 
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Jack@European_Parts

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Intermittent OXS sensor heater or short and causing limp mode while no code due to tune with deletes or faulty sporadic N75 or diverter valves not sealing, maybe faulty ECU?

Did you isolate components & perform manual test of WG and bypass vales for mechanical function? .........JPPSG
 
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dafrazi

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The problem you're describing was a common symptom of a failing TBB on the y-pipe. Cheap fix to try.
 
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Samz09

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The problem you're describing was a common symptom of a failing TBB on the y-pipe. Cheap fix to try.
Absolutely the Throttle body boot on these can be a real pain in the butt. Either with a tear in it, or coming off the TB or the plastic intercooler pipes popping out. Especially if you've installed a silicone one thats become oil soaked, along with wider clamps that usually push the pipes out some when tightened, and when boosted, along with being oily, the "POP" happens when you boost. This comes back to did you have it smoked tested with a legitimate machine, or at least a shop do it to have a for sure answer.

Very good point, but id add with that, you would have a very distinct hissing noise, close to no boost pressure and or eventually a cel. However maybe the map sensor attached to it could be oil soaked giving incorrect readings. But you said you've changed, maf, map, front 02's.

Maybe im reading it wrong or dont understand the abbreviation's in your parts replaced list. When the turbos were replaced, were new Turbo oil feed lines installed? either oem or SS braided lines? Everyone with a 2.7 knows the oil feed lines are the #1 cause of turbo failure and boost spikes since they slug up. Maybe i missed the post about it but better safe than sorry
 
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