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Thread: 2001.5 Audi S4 Limpmode with no CEL

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    2001.5 Audi S4 Limpmode with no CEL

    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=19Q...QBmUOEgFHbCB_Y

    Vag-Com Logs (4runs): https://drive.google.com/open?id=1N6...w6a2OtroZTgMgk

    Readiness log: https://drive.google.com/open?id=1e9...6oLz6_krA2_lt6
    Last edited by LimpMode; 09-05-2019 at 09:44 AM.

  2. #2
    Benevolent Dictator Uwe's Avatar
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    These links all produce 404 errors. Please post your data in-line. It's just text. Copy & paste it.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Quote Originally Posted by Uwe View Post
    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
    www.Ross-Tech.com
    
    
    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
    www.Ross-Tech.com
    
    
    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
    Last edited by Uwe; 09-05-2019 at 02:12 PM. Reason: CODE tags

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  5. #4
    Benevolent Dictator Uwe's Avatar
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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-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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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?

  7. #6
    Benevolent Dictator Uwe's Avatar
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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-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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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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    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by Samz09 View Post
    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-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Quote Originally Posted by Uwe View Post
    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

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  13. #10
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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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