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Mot fail due to emissions, possible causes?

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  • #16
    The turbo seems to be leak free for now Oil return flows free and there is no excessive crankcase pressure. It seems that the oil change cured my leaking issues.

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    • #17
      What kind of cat do you have, originals or aftermarket? How are the exhaust manifold flanges, any signs of leaks? Everything tightened up as they should be? Even a small leak on the exhaust side before the lambda probe can cause problems with emissions. Twin tip exhaust pipes can cause problems unless you block the pipe without the MOT probe.

      No fault codes of any sensors? Air temp, water temp, knock sensors, engine feel healthy when driving? Do you have a wideband lamdba gauge?

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      • #18
        Aftermarket catco cat is what I currently have.

        There should not be any leaks before the
        lambda. All new turbo seals were fitted when it was out along with copper locking nuts.

        Only fault code I had was about the intermittent idle speed adaptation. I will recheck the codes.

        The engine feels good to me but I have no comparison to any other S2.

        No wideband lambda yet.

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        • #19
          Antsa,

          Although I don't have this engine, I thought that a) you may have too much fuel at idle; b) the ISV is trying to correct, but is (intermittently?) maxed out; and c) these three things (common between a 7A and your motor) done in the order below, might be easy enough to check first:

          - Try a code clear and pull again to confirm presence now. Is the code you got before this one?:

          2231 (Blink Fault Code), 00533 VAG1551/2 Fault Code Number
          Idle Speed Control Valve (N71)
          Idle speed adaptation maximum limit exceeded or Minimum adaptation limit not reached
          Sticky or binding ISV, Mass Air Flow Meter (G70) offset, additional air introduced between G70 and N71
          Symptom: Idle speed too low, or too high, Add air leak.

          How is the idle speed, fast, slow, smooth?

          - Do a check of engine vacuum as delivered to the FPR at warm idle (see info at Dave's links going back);

          https://www.s2forum.com/forum/techni...58#post1234758

          - Could the ISV, MAF and connectors use a clean? Are your injectors all closing properly and not leaking while under pressure?

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          • #20
            Originally posted by Lago Blue View Post
            Antsa,

            Although I don't have this engine, I thought that a) you may have too much fuel at idle; b) the ISV is trying to correct, but is (intermittently?) maxed out; and c) these three things (common between a 7A and your motor) done in the order below, might be easy enough to check first:

            - Try a code clear and pull again to confirm presence now. Is the code you got before this one?:

            2231 (Blink Fault Code), 00533 VAG1551/2 Fault Code Number
            Idle Speed Control Valve (N71)
            Idle speed adaptation maximum limit exceeded or Minimum adaptation limit not reached
            Sticky or binding ISV, Mass Air Flow Meter (G70) offset, additional air introduced between G70 and N71
            Symptom: Idle speed too low, or too high, Add air leak.

            How is the idle speed, fast, slow, smooth?

            - Do a check of engine vacuum as delivered to the FPR at warm idle (see info at Dave's links going back);

            https://www.s2forum.com/forum/techni...58#post1234758

            - Could the ISV, MAF and connectors use a clean? Are your injectors all closing properly and not leaking while under pressure?
            I cleared the idle speed adaptation code a few days ago and it seems to be gone for now.

            To me the idle seems smooth, around 750 rpm when warm.

            The vacuum to the FPR has to be tested.

            MAF and its connectors were cleaned last summer.

            About the injectors, I can't say for sure. If replacing the catalyst does not solve the problem my next step is to take the injectors out for a checkup.

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            • #21
              I got a sports cat installed 200 cell. Only i had the car mapped with a different ecu and i can switch maps. I have an eco map which helps me get through MOTs

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              • #22
                This is now sorted, new catalytic converter did the trick. The car now has mot

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                • #23
                  Originally posted by Antsa View Post
                  This is now sorted, new catalytic converter did the trick. The car now has mot
                  Good man!!! awesome!!! bet you are happy!

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