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Thread: MOT emissions failure (CO only)

  1. #1
    Goron goron Kumagoro's Avatar
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    MOT emissions failure (CO only)

    Hello,

    I took my Saxo 1.4 VSX (1997) in for an MOT and it failed on emissions both
    times. The first MOT passed the CO test at natural idle but failed the fast
    idle tests. The second time I put some redex in a full tank and drove about
    200 miles ragging it quite a bit (this got the tank down to about halfway)

    Before I took it in I then filled it right up again, so still some redex in the
    system. I drove it hard for several miles right before the test as I did before
    also and also took the air filter out. Unfortunately it failed again only worse
    this time.

    Below are the results of both MOT tests

    ==============================================
    FIRST MOT TEST

    Fast idle Test

    CO = 0.61% (Limit 0.3) FAIL
    HC = 25 ppm (limit 200) PASS
    Lambda = 1.002 Limit (1.03) PASS

    2nd Fast Idle

    CO = 0.56% (Limit 0.3) FAIL

    HC = 18 ppm (limit 200) PASS
    Lambda = 0.997 Limit (1.03) minimum limit is 0.97 PASS

    Natural Idle Test

    CO = 0.47 (limit 0.5%) PASS

    ======================================



    =======================================
    2nd MOT results

    Fast idle Test

    CO = 0.68% (Limit 0.3) FAIL
    HC = 39 ppm (limit 200) PASS
    Lambda = 1.002 Limit (1.03) PASS

    2nd Fast Idle

    CO = 0.45% (Limit 0.3) FAIL

    HC = 71 ppm (limit 200) PASS
    Lambda = 1.011 Limit (1.03) minimum limit is 0.97 PASS

    Natural Idle Test

    CO = 0.68 (limit 0.5%) FAIL

    ===========================================

    Now can anyone tell me what the likely cause of the failure is?
    Did the redex do it in? did not having an air filter actually make it worse?
    did ragging the car at high revs do it in?

    Before the first test I changed my lambda sensor for a new bosch one.
    The old one had silicon on it back from the dodgy tesco fuel (in 2007).
    Also I had a new (although cheap) catalytic converter fitted about 8
    months ago. Could the lambda sensor being crap have damaged the CAT?
    I changed the spark plugs around the same time too.

    The fuel efficiency is good at about 45 MPG. Its done about 75k

    Other problems with the car,

    I feel that it lacks power compared to what I expected, it feels like it has
    less power than my old 1.2 clio.

    When pulling away and accelerating in first and second it sometimes
    doesnt go and pauses a bit a few times. The revs dont jump up so
    I dont think its the clutch slipping... Also very rarely the rev counter
    isnt very smooth when letting off the power and jumps down say to 2500
    to 1500 then to 1000.

    If anyone can give me some idea of whats wrong I would appreciate it
    as I am not sure what to do about it.

    Cheers

  2. #2
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    Re: MOT emissions failure (CO only)

    go get it read for fault codes, may be a bad airflow sensor, camshaft sensor or one of the other sensors if you changed the O2 sensor.

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    Banhammer in peace PeterB kalniel's Avatar
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    Re: MOT emissions failure (CO only)

    (Not an expert)

    I'd have thought CO would increase if you don't get enough air in the fuel/air mix. Using redex would clean your fuel injectors, possibly increasing the amount of fuel without also increasing airflow, thus could increase CO emissions.

    So to fix I'd concentrate on things affecting airflow and the fuel/air mixing - the sensors Barney mentions for example.

    The pausing on pulling away could be airflow related, or also water getting into the mix somewhere.

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    sneaks quietly away. schmunk's Avatar
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    Re: MOT emissions failure (CO only)

    1997, you say? Have you owned it at least 12 months...


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    Re: MOT emissions failure (CO only)

    Quote Originally Posted by schmunk View Post
    1997, you say? Have you owned it at least 12 months...
    With a valid MOT.. ah..

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    Goron goron Kumagoro's Avatar
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    Re: MOT emissions failure (CO only)

    thanks for the replies.

    I couldnt afford a new car anyway hahaha.

    With regards to air flow I took the air filter out which should increase the air flow alot
    but obivously it didnt work out that way. I have been told on other forums that it
    is likely to be the cheap ass CAT. Especially as its only CO and not HC.

    I will take it to the garage i got the cat from and they can do the MOT as well that. Then if
    they say it needs a new CAT i will tell them I want my money back for the old one.

    If anyone else has some suggestions let me know.

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    Re: MOT emissions failure (CO only)

    as i said, get the codes read incase somethings faulty

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    Re: MOT emissions failure (CO only)

    My punto failed it's MOT on emissions, so I stuck the original air filter back on (had an aftermarket K&N one on before) and it passed ok. Although I did notice there was a split in the breather pipe which I repaired at the time so it could of also been that.

  9. #9
    Larkspeed
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    Re: MOT emissions failure (CO only)

    I'm assuming you can't use the old trick of cranking down the air fuel mixture and making it run really lean for the test.

    It will have crap for power but once through the test you can turn it back up again.

    Also if the "cheap assed cat" you bought is not type approved then that could very well be the cause of your problems as it is not doing the job properly. Also if it is not type approved it is actually illegal to be using it for road use and carries huge fines.

    Here we can't even buy cats that are not type approved but I know for a fact you can in the UK some garages use them to get away with charging high for low grade parts.

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    But Why's It So Cold?. jon bda's Avatar
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    Re: MOT emissions failure (CO only)

    Quote Originally Posted by Larkspeed View Post
    I'm assuming you can't use the old trick of cranking down the air fuel mixture and making it run really lean for the test.

    It will have crap for power but once through the test you can turn it back up again.

    Also if the "cheap assed cat" you bought is not type approved then that could very well be the cause of your problems as it is not doing the job properly. Also if it is not type approved it is actually illegal to be using it for road use and carries huge fines.

    Here we can't even buy cats that are not type approved but I know for a fact you can in the UK some garages use them to get away with charging high for low grade parts.



  11. #11
    Larkspeed
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    Re: MOT emissions failure (CO only)

    lol I did not even notice the last post date

  12. #12
    Goron goron Kumagoro's Avatar
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    Re: MOT emissions failure (CO only)

    Ironically though I have made another thread about the same thing (although a couple of years later) a little while back.

    It failed on the same thing, CO again, I got a new cat but it made no difference so it started making me think something else is up. I have been advised though that this new cheap cat (from euro car parts) is well crap and I need to get a better one but because my car is pre type approved they dont make any type approved ones. So I have to get an expensive one from Citroen and then it might not actually be that.

    When I had it tested last though they said my lambda was all over the place (we suspected a leak some where but couldnt find any) we checked the vacuum pressure and it was fluctuating around 17. We took it to get a code check and they said there a couple of the tappets were too tight. Well we loosened them up and now the vaccum is at 20 which is better and a lot more stable and the reading on the lambda sensor is also a lot more stable. Is that enough to get it through the MOT though I dont know. I think I will risk it again and if it fails go for an expensive CAT.

    Apparently old saxos and 106s are known for this trouble. I will report back to say if it worked or not for those that may find this while googling.

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    Re: MOT emissions failure (CO only)

    Years with the same issue? Save and buy a different motor!!

    Most definitely the cat causing the issues there, unless your running rich(Whats the exhaust fumes look like? thick? thin? white? black? blue? etc). I don't know much about 1.4 engines, but you could run it lean as said and give that a shot, it will even out the air/fuel ratio and if its running rich already it might do it a favour!

    With cats, they give up a lot, especially cheap ones that cannot handle the job they were made for. You could head down a local scrappy and find a similar car and steal the cat off that, hope it works (just enough to get through the mot) and it will be cheaper than buying a new one straight from citreon!

    Alternatively, word on the street is, that 'certain' garages are quite....'lenient' on emissions. But I would not know anything about that because my car is most definitely not running a decat with 4-2-1 manifold etc.

    Let us know how you get on

    p.s change oil/air filter/spark plugs + oil filter. That can have good effects

    P.s. 2 months ago is not bad in a dead forum section
    Quote Originally Posted by Stoo
    ...and it's *slow* - really slow, slower than a really slow thing swimming through treacle, one handed, and only kicking with one foot.

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