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2.0 TDI CR / CBBB Rough Idle

Discussion in 'A3/S3/Sportback (8P Chassis)' started by BenC00, Jul 19, 2013.

  1. BenC00
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    BenC00 Member

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    I am experiencing rough idling for the first 5-10 minutes of the engine running. Car is a 2009 8P3 2.0 CR TDI (Engine code CBBB).

    VCDS is showing no faults, and the issue doesn't appear to happen each time the car is started from cold making it hard to troubleshoot and diagnose.

    I will try to monitor injector figures in VCDS when the issue happens again but can anyone tell me if the 2.0 TDI CR engine is affected by the Injector Loom failure that I've read all over the internet? (they all reference PD engines, not CR)

    VAG TDi Injector Problems - PistonHeads

    There appear to be lots of threads on the forum for this but nothing mentions Common Rail engines, only PD.

    Any advise or information appreciated :)
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  2. NHN
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    Has it had a cambelt done yet?
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  3. BenC00
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    BenC00 Member

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    Not had the cambelt changed yet, i guess it must be coming up for renewal as the car is almost 5 years old now with 50,000 miles on the clock. (Cambelt change : Volkswagen UK)

    Do you really think that this could be causing the problem?

    Is there anything that i can check in VCDS whilst the car is running to tell me if the timing is out?
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  4. BenC00
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    I forget to mention that the lumpy / rough idling doesn't always happen, it seems to be 2 or 3 times out of 5.

    If someone could point me in the right direction in VCDS then i could have a detailed look into it before i book it in at Audi. :salute:
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  5. BenC00
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    BUMP! ... anyone? I've looked through VCDS Wiki and can only find information for timing relating to PD engines :(
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  6. gupsterg
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    gupsterg Active Member

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    Hi mate :) ...

    I'd look at EGR/AIR MASS MVB's you could have an EGR fault which is sending AIR MASS out of spec thus idle rev fluctuation ...

    I had the same headache with a 3.0 TDi V6 CR on an A6 ...
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  7. BenC00
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    Thanks mate :)

    I'll take a look next time it is idling strange and update this post. :racer:
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  8. BenC00
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    I forgot to ask... what sort of values or what should I be comparing values against in order to determine if my EGR is faulty?
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  9. gupsterg
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    This is a screen capture video of mine when fault was occurring, I overlayed the red text via Nero Video editor ...

    This has been the best capture of event ever [​IMG]... after 5-6 sec you will see a swing down to 777RPM then regular up/down of 777RPM-819RPM...



    You will have a specified value for (x) that is what engine ECU want, actual is what a sensor is reading for (x) ...

    Now due to there being no detection on my engines EGR valve open/close all it show is a value for how much the ECU is asking it to open ie the 90%+ is closed and lower values are open ...

    So I know air mass specified/actual is out from MVB data, EGR is being requested to open, so if air mass out of spec I must run investigations on i) charge air system ii) EGR . As my charge system had no faults on hoses/intercoolers the EGR was left to sort :) ...

    Firstly google, download and study :-

    SSP403 2.0 TDI Engine with Common Rail

    SSP420 Audi 2.0-litre TDI Engine with Common Rail Injection System

    Should be first hits on google if search above text, on SSP 403 view pages 46 & 47, SSP 420 48 & 49 for EGR ...

    You'll find plenty of great info relating to tech/fundamentals in those files with graphics :D ...

    Here is a list of MVB labels/info for your engine Link:- Audi Portal: ECU Diagnostic . Audi A3 8P (2003- ) . Engine Control Unit J623

    I'd start with looking at MVB 03 10 20 or 21 ...

    This is the software which you can use to capture VCDS screen then host via youtube and post :D ... Link:- FastStone Screen Capture - The Best Screen Capture Software
    Last edited by a moderator: Aug 15, 2014
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  10. BenC00
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    Thanks mate, much appreciated :)

    I'll take a look this weekend to see if I can figure it out.

    I have never cleaned my EGR and the car has covered 50k so I guess it could do with being replaced or cleaned....
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  11. BenC00
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    Here is a screenshot of VCDS showing Injection Quality across all 4 cylinders... the engine was warm, is it normal for it to differ than much across the 4 cylinders?

    [​IMG]

    I'll move onto MAF & EGR next....
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  12. gupsterg
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    gupsterg Active Member

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    To me they seem in spec ... cylinder to cylinder there will be a difference, why?

    You are looking at smooth running control of engine in that MVB, the ECU is taking data from a crank angle sensor to assess what fuel injection quantity/timing to do so it runs smooth ...

    This is a very good video to watch Link:- AUTOINFORM ONLINE MAGAZINE: Common Rail Diesel Smooth Running - YouTube
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  13. BenC00
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    Thanks for the very useful link :)
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  14. gupsterg
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    I'm glad you liked it and found useful :icon_thumright: , those videos helped me a lot as well ...

    Frank Massey has done some others on youtube as well and also reading stuff here I found good Link:- Autoinform
    Last edited: Aug 9, 2013
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