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Thread: Unable to diagnose 1998 Polo "one day no power, unable to idle, VAG-COM has no codes"

  1. #1
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    Unable to diagnose 1998 Polo "one day no power, unable to idle, VAG-COM has no codes"

    Hi to you all from a newbie in Australia

    Got my shiny new VAG0COM to help me track down the problem that suddenly appeared in my Polo. I'm working through the VAG-COm capabilities but there is a LOT there, hope someone can point me in the right direction..

    -----------------------------
    History (1998 Polo 1.6 lkitre, auto, 6N1):
    Car has 92K Kms on it, has never had a problem with running, power, starting, etc One day at startup, it had very little power, would not idle below 1100, barely moved on the road (like a dead cylinder perhaps, in the level of power reduction happening) and could go no more than ~5-10 kph, I had to select lower gears to get that too. Easily stalled out if I did not keep the revs up. I was able to move it to a place to work on it out the back of my place, but lots of stalling and nearly didnít make a very minor hill, the power was so poor. In summary, one day with no warning (I have done my own diagnosis and repair work on many cars across every system (except transmissions) since the 70ís, I am very alert ti changes in engine function - so this was not a gradual slide into a problem, it just happened suddenly one day at startup. Very weird to be so hard to diagnose / correct....

    What I've done:
    Battery disconnected for a month while away. Returned and re-connected and ...
    Started fine again. Runs well above ~1600rpm, it feels and sounds fine there and higher. This was what I had found myself left with before going away for a month.
    If allowed to drop to 1000 rpm (taking foot off accelerator) - it hunts around across a range of a few hundred RPM, producing rough idle to smooth, engine lifts and drops rpm, gets rough, gets smooth, and so on. No obvious pattern to what is happening with the ups and downs though.
    The car progressively seems to try to lower rpm by itself, this also brings increased roughness mostly. Like having one cylinder running very badly (but plugs show no issues). It then went to ~900 RPM and was rough then smooth (as if under ? ECU? control, was not consistent like if there was a vacuum leak). Then went a bit lower, hunted around again showing variously smooth then rough idling. Then a little lower and the same thing. Then after about 4 mins it dropped lower to about 500 rpm and stalled out.
    But on scan with my new Ross Tech VAG-COM I get no codes at all, before or after trying things / running for a while. The battery is well charged and have tried all this after battery disconnect / reconnects, no effect.
    Trying again today after being away, starts fine but drops to a very rough 600-700 rpm, sometimes up to 900, but variously rough then smooth idling. Keeps going for a few mins then dies as before.
    If it was an old style carby Iíd be thinking idling jets, but this is an electormechanical throttle control system.

    What should I be looking at next? Iíve tried a few things, oith no change to the outcome...

    Checked and cleaned the injectors (all fine)
    Replaced the lambda sensor in the exhaust pipe
    Spark plugs replaced (no differences in appearance to suggest cylinder issues)
    Have cleaned the existing throttle body.
    Tried another throttle body (wreckers).
    Tried another ECU (wreckers).
    Have not replaced fuel filter as that does make sense - it runs well at high rpm (i.e high fuel flow).
    Tried throttle adaptation as per the Ross Tech wiki/ website video (both 001 and 098 codes, and 001 is not the adaptation code on this model), it failed to do anything, and it shows weird and very high starting values for the throttle pots:
    Address 01: Engine (032 906 030 S)
    10:09:10 Group 098: Throttle Control Basic Setting
    128.0 Throttle Pot G69 Voltage 0.500...5.00V
    119.0 Throttle Pot G88 Voltage 0.500...5.00V
    53.0 Operating Mode
    25.0 Adaptation Status Idle/OK/ERROR

    Nothing tried with the VAG-COM with the engine ďrunningĒ :-)

    So, in the absence of any VAG-COm codes coming up, and the Adaptation not working, Iím a bit lost. It definitely seems like it is a throttle reset /adaptation issue not being resolved ATM, but I am new to this area.

    What might the the high 098 Throttle Pot values mean for me? Any suggestions for next steps?

    Thanks,

    David Parsons
    Adelaide, Sth Australia

  2. #2
    Benevolent Dictator Uwe's Avatar
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    Hi and welcome. It might be helpful if you'd post a scan even if there are no fault codes. The scan will show people exactly what ECU you've got.

    -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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    Thanks Uwe, will do.

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    Here is the full autoscan for the Polo, hope it can assist anyone with ideas on what's going on here
    Thanks in advance for any input...
    Cheers
    David

    Code:
      Monday,11,November,2019,17:24:55:61186
    VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
    VCDS Version: 19.6.2.0 (x64)  HEX-V2 CB: 0.4508.4
    Data version: 20190930 DS308.0
    www.Ross-Tech.com
    
    
    VIN: WVWZZZ6NZWW084210   License Plate: POLO SCAN
    Mileage: 92110km-57234mi   Repair Order: _11-11-2019
    
    
    
    --------------------------------------------------------------------------------
    --------------------------------------------------------------------------------
    
    
    Chassis Type: 6N - VW Polo (1995 > 2002)
    Scan: 01 02 03 08 15 17 19 25 41 45 46 55 56
     
       Mileage: 92110km-57234miles
    -------------------------------------------------------------------------------
    Address 01: Engine        Labels: 032-906-030-AEE.clb
       Part No: 032 906 030 S
       Component: MARELLI 1AV        2138  
       VCID: 1A6DD552F58149F7273-4B00
    
    No fault code found.
    Readiness: N/A
    
    -------------------------------------------------------------------------------
    Address 02: Auto Trans        Labels: None
       Part No: 001 927 749 D
       Component: AG4 Getriebe 001    0215  
       VCID: 1B63D056FABB30FF3C5-508A
    
    No fault code found.
    
    -------------------------------------------------------------------------------
    Address 15: Airbags        Labels: 1J0-909-60x-VW3.lbl
       Part No: 1J0 909 603 E
       Component: AIRBAG VW3 -        V03  
       Coding: 00069
       Shop #: WSC 01319  
       VCID: 2B030096AA1BC07F4C5-4B5C
    
    No fault code found.
    
    -------------------------------------------------------------------------------
    Address 17: Instruments        Labels: 6N0-919-xxx-17.lbl
       Part No: 6N0 919 861 E
       Component: KOMBIINSTRUMENT MMO V06  
       Coding: 02741
       Shop #: WSC 00000  
       VCID: 3B2330D65A7B50FFDC5-51F2
    
    No fault code found.
    
    -------------------------------------------------------------------------------
    Address 25: Immobilizer        Labels: 6H0-953-257.lbl
       Part No: 6H0 953 257 
       Component: IMMO VWZ3Z0V7086171 V64  
       Coding: 09600
       Shop #: WSC 00000  
       VCID: 6D87CE8E548F0E4F121-4B1E
    
    No fault code found.
    
    End----(Elapsed Time: 02:48, VBatt start/end: 11.6V/12.0V. VIgn 0.0V)------
    Last edited by Uwe; 11-11-2019 at 08:49 AM. Reason: CODE tags

  5. #5
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    Whats the intake vacuum level when it does idles badly.

    Also is it Fly by wire or cable throttle?

  6. #6
    Benevolent Dictator Uwe's Avatar
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    1998 is almost certainly still a cable throttle.

    It might be worth trying Basic Settings in Group 001 on this ECU. Coolant temperature should be at least 80įC when doing that.


    -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.

  7. #7
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    Uwe, Ran at > 2000 rpm for coolant temp over 80C.
    Tried 001 and (immediately) no effect on "GO".
    Also 098 again, no effect.
    Found a ref to vacuum being block 204, tried that but it's the default 'nothing there" standard set of numbers that comes up.

    I have spent 10 mins trying to upload screen-shot images of the VCDS screens for things I tried so the details / numbers are there, but can't work it out, seems only an image with a URL can be uploaded. I have a word doc, or jpg's, with the screen info - am I missing something simple here for pasting images into these windows?
    Cheers
    David

  8. #8
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by platydog2 View Post
    I have spent 10 mins trying to upload screen-shot images of the VCDS screens for things I tried so the details / numbers are there, but can't work it out, seems only an image with a URL can be uploaded. I have a word doc, or jpg's, with the screen info - am I missing something simple here for pasting images into these windows?
    Yes, we don't allow image uploads here. Please see How to Post Pictures.

    -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.

  9. #9
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    Thanks, did not see that limitation, and has always wandered what imgur was :-)
    Here's the images:
    https://imgur.com/zVdmx4R


    and
    https://imgur.com/O1wwsuB


    Hope this posting works
    David
    Last edited by Uwe; 11-13-2019 at 09:00 AM. Reason: IMG -> URL & added in-line images

  10. #10
    Benevolent Dictator Uwe's Avatar
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    Quote Originally Posted by platydog2 View Post
    Hope this posting works
    I fixed it for you. Click "Edit Post" to the above post to see what I did. In order for IMG tags to work, you must link to an actual image file, generally something that ends in .jpg or .png.

    -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.

  11. Likes platydog2, PetrolDave liked this post

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