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NEED HELP: Failed emissions test

AudiB720TS Aug 8, 2018

  1. AudiB720TS

    AudiB720TS Member

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    Today I was going to pass MOT and use it as the start for my turbo project.
    Instead the car failed testing. Overall they said the car was in perfect condition, but they fail it because of the emissions tests. I now have 30 days to pass a retest or I am not allowed to drive the car. Needless to say, I won't be buying parts for my new project until the car is road worthy again.

    You guys have similar tests and thresholds, referring to "EU 82.1.2" standards.
    • CO value at idle speed: 0,4 (0,3 is highest permitted value)
    • CO value at fast idle speed (2.500 RPM): 0,5 (0,2 is highest permitted value)
    NOTE: other exhaust emissions values were within range: Lambda 1.0 (0.97 - 1,03), HC 68 (200).

    My thinking is that 02 sensor(s) is OK because other values are good, and car runs really well. I am running a 034 Motorsports high flow cat, could that be the issue? Has anybody passed MOT with this cat before? On the other hand, my old WRX STI passed with a 100 cell cat without a problem. The cat was warm prior to test - I had driven aggressively for almost an hour just before the test so it was absolutely at good working temperature.

    More info:
    - Oil change and engine flush, late 2017
    - New spark plugs (June 2018)
    - Runs on Shell V-Power
    - HFC at working temperature during test

    Any and all help welcomed!


    EDIT: My lambda is 1.0 which is a perfect 14.7:1 air to fuel ratio. That should mean that my mixture is OK (good actually), right!? Meaning its an issue with the HFC not reducing the CO's.
     
    Last edited: Aug 8, 2018
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  3. DieselJake

    DieselJake Well-Known Member VCDS Map User

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    Was the car warm when they tested it? Best to get it up to tempreture and give it an "Italian style tune up" before an MOT, failing that get it tested somewhere more friendly.
     
  4. Metalsmurf

    Metalsmurf Member Team Dolphin Grey TFSI Owners Group Audi A4 Audi Avant Owner Group quattro S-line owners group Manual

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    I failed mine about a month ago, exactly the same. But standard Cat. Took it for a thrashing and passed no problem afterwards. Bit worried now as I'm going to put my 034 cat on next week.

    Sent from my SM-G955F using Tapatalk
     
  5. AudiB720TS

    AudiB720TS Member

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    It was VERY warm. Had been driving fast on lower gears.

    Might not be the cat. Could be the JHM stage 2 tune. I found this explanation on CO (google translated):

    "CO is formed when oxygen is insufficient during combustion. High carbon monoxide levels (measured as a percentage of exhaust gases) may be caused by excessive mixing, low idle speed, incorrect float level, clogged air filter, poor operating PCV valve, or incorrectly set gasification or injection. Low oxygen levels indicate that there is more fuel than can be consumed with the oxygen available. This may be called acid deficiency. The solution is to reduce the amount of fuel"
    Going by that: my air filter and is fine (its new). Idle speed is good. PCV does have a catch can but that should improve values IMHO.
    So I would guess that the tune I am on is too "fat". I can't change program on the ECU though.

    Would adding E85 help?



    EDIT: My lambda is 1.0 which is a perfect 14.7:1 air to fuel ratio. That should mean that my mixture is OK (good actually), right!? Meaning its an issue with the HFC not reducing the CO's.
     
    Last edited: Aug 8, 2018
  6. Metalsmurf

    Metalsmurf Member Team Dolphin Grey TFSI Owners Group Audi A4 Audi Avant Owner Group quattro S-line owners group Manual

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    Best bet is to put the standard Cat back on for the test, however if I had to do that every time I would get rid of the hfc and just straight pipe it.

    Sent from my SM-G955F using Tapatalk
     
  7. Dan_Avant

    Dan_Avant Active Member

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    Check your MAF and MAP sensors are working properly.

    I had the same issue. Changed my MAP sensor and cleaned the MAF and it got me through MOT
     
  8. AudiB720TS

    AudiB720TS Member

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    Hi Dan,
    When you say you had the same issue, can you confirm you had good lambda value but poor CO?
    How did you conclude you had an issue with MAP/MAF?
     
  9. Jon13s

    Jon13s Member

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    Mine has a 034 cat in and fails unless its really hot. Interested to see if there's something that has an effect on it.

    Sent from my SM-A520F using Tapatalk
     
  10. Just Rob.

    Just Rob. Moderator Staff Member Moderator Team Brilliant Black Team Daytona TFSI Owners Group Team V8 VCDS Map User Gold Supporter Audi RS4 Audi A4 Audi Avant Owner Group quattro S-line owners group Manual

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    just a bit from me, I fitted a 034 to my old bus and it passed no problem , well within specs but it is with the standard oem system just a larger dia down pipe, maybe it is more an issue with after market systems connected to the sports cat, just a thought.
     
  11. AudiB720TS

    AudiB720TS Member

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    I talked to my mechanic last night. He will test my emissions again next week.
    Prior to that I will do some maintenance on the car. If it fails his test, I'll have him install the OEM cat, take it to MOT and then reinstall the HFC.
    Talked to JHM as well: they said it would be OK to run the Stage 2 program with stock cat provided I'm not racing the car.
     
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