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Pass Emissions for MOT ?

edited 30 November -1 at 1:00AM in Motoring
21 replies 100.9K views
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  • PssstPssst Forumite
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    The emissions check should be done when the oil temperature has reached a minimum temperature. MoT testers should insert an oil temp probe into the engine usually via the dipstick hole. Only then should the test be completed. It is unusual for a modern car with an ECU/fuel injection system to fail on emissions. My near 17 year old Golf has never failed on emissions.
  • NileNile Forumite, Board Guide
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    I'll move this thread to the 'Motoring & Public Transport' board.

    Hi, Martin’s asked me to post this in these circumstances: I’ve asked Board Guides to move threads if they’ll receive a better response elsewhere(please see this rule) so this post/thread has been moved to another board, where it should get more replies. If you have any questions about this policy please email [EMAIL="abuse@moneysavingexpert.com"][email protected][/EMAIL].

    Nile
    Hi, I'm the Board Guide on the In my home (includes DIY) and the I wanna buy-it or do-it boards which means I volunteer to help get your forum questions answered and keep the forum running smoothly. However, do remember that Board Guides don't read every post. If you spot an inappropriate or illegal post then please report it to [email protected]. It is not part of my role to deal with reportable posts. Any views are mine and are not the official line of moneysavingexpert.com.

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  • edited 4 May 2009 at 11:47AM
    anewmananewman Forumite
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    edited 4 May 2009 at 11:47AM
    Pssst wrote: »
    The emissions check should be done when the oil temperature has reached a minimum temperature.
    I believe they check the coolant hoses are hot and if it passes then it's passed. If it fails then I believe they check the oil temp and perform a slightly different emissions test.

    When thrashing a car you don't need to go fast, just use lower gears and rev the engine a bit harder - best to wait till the engines warmed up a bit first before thrashing it though. I would put a double dose of redex in the petrol tank (petrol injection variety if for a petrol injected model). If this doesn't work then you'd be starting to look at the temperature sender (though if this failed there'd usually be noticeable running problems), then the more expensive Lambda sensor, or even the more expensive still catalytic converter.

    Cleaning things under the bonnet may well make things look nicer, and stop the car from starting and damage expensive electrical components if done incorrectly, but won't reduce emissions :)
  • edited 5 May 2009 at 2:17AM
    asbokidasbokid
    2K posts
    edited 5 May 2009 at 2:17AM
    things to do if your car fails the emissions part of the MOT test..


    new sparkplugs - about £8 for a set of standard quality

    new HT leads - about £25

    new air filter - about £6

    check the ignition timing - a cheap strobe gun costs about £10 to DIY.

    new lambda (O2) sensors - these sensors can be bought for £10 in a universal form and then spliced onto the proprietary connectors used in the car

    new catalytic converter - around £30 - £50 for most popular cars

    reset the car's ECU to clear any memorised engine faults. Typically, when an engine fault occurs, the engine's computer (the ECU) runs the engine in 'limp mode'.

    When the engine is running correctly, the ECU normally adjusts the fuel-air mix on a dynamic basis, according to data received in real-time from the engine sensors.

    However, when the engine is crippled and running in limp mode, the ECU uses a static table of data for fuel-air mapping. This is inefficient and can cause excessive exhaust emissions.

    Obviously it is sensible to remedy any engine fault, but some faults can be transient, or one-offs (e.g. a temporary electrical sensor fault is often triggered by driving through a flood).. However, these faults may still be memorised by the ECU, affecting the overall efficiency and performance of an otherwise healthy engine.

    Resetting the ECU could clear these faults, and help your car to pass the MOT emissions test.
  • vaiovaio Forumite
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    asbokid wrote: »
    things to do if your car fails the emissions part of the MOT test……….
    ………new catalytic converter - around £30 - £50 for most popular cars

    I think you are missing a zero here
    Dangermac wrote: »
    I agree with you......

    DM
  • edited 5 May 2009 at 2:10AM
    asbokidasbokid
    2K posts
    edited 5 May 2009 at 2:10AM
    vaio wrote: »
    I think you are missing a zero here

    cats for many popular cars are available for under 50 quid..

    http://www.cats-direct-shop.co.uk/

    i would expect the fitting cost to be under £20 including any new gaskets needed.
  • vaiovaio Forumite
    12.3K posts
    thanks for the link, way cheaper than I thought
    Dangermac wrote: »
    I agree with you......

    DM
  • edited 5 May 2009 at 10:52AM
    anewmananewman Forumite
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    edited 5 May 2009 at 10:52AM
    Problem is the cheapie cats will have failed come next MOT. Better to buy the OE one if you want it to last. Often similar for the Lambda sensors, but if you look on Ebay Bosch ones can be gotten hold of relatively cheap (compared to Mfr's prices).

    Bad HT leads would usually reveal themselves in running problems or obvious sparks when the running engine is viewed in the dark.

    Timing is usually handled by the ECU now so a strobe gun is useless. There are usually just marks to line up, and these would only be incorrect if a timing chain had stretched for example.
  • edited 6 May 2009 at 11:48AM
    asbokidasbokid
    2K posts
    edited 6 May 2009 at 11:48AM
    anewman wrote: »
    Problem is the cheapie cats will have failed come next MOT.

    Funny.. a local motor factors said that to me four years ago... but my £28 cheapo catalytic converter is still going strong.. I've grown fond of that cat! It follows me from car to car!

    I actually showed the motor factors my £28 "cheapie cat", and pointed out to them that the quality of the steel it is made from is superior to their own cat for sale at £200+ !! Ahh, they claimed! That's as maybe, but it will still be crap on the inside, they said!

    Well, four years on, that's proven not the case.. The factors came back to me later, to ask for the contact details of the place i had gotten the cheapo cats from.... I wonder why........
    Better to buy the OE one if you want it to last.
    You have some unequivocal MTBF data to actually show that? Thought not!

    As I'm sure you're aware, that company (Sutton Auto Factors) has been selling discount car parts for decades.

    As well as discount catalytic converters, they sell all manner of other vehicle components.. brakes, suspension, steering, drivetrain, fuel and ignition components, filters.. you name it, they've got it..

    most of their cats come with a two year warranty and the company sells well known brands of all exhaust components, including Timax, Arvin and Belton Massey...

    And shipping is an astonishing £7.50 whatever you buy... I feel slightly embarrassed when the delivery man staggers in with an eight foot length of centre pipe, shipped across the country for just £7.50.

    I got another story about the ever-friendly local motor factors and his desperate protectionist claims that his online rivals are selling crap and dangerous car parts..

    Well, we were getting wishbones (lower suspension arms) from Suttons.. they were branded Quinton Hazell (a well respected make), and cost about £50 each instead of the £190 demanded by the local factors.. The local factors got so desperate, they actually started spinning a tale that the wishbones were fake QH!
    Often similar for the Lambda sensors, but if you look on Ebay Bosch ones can be gotten hold of relatively cheap (compared to Mfr's prices).
    Ahh, that old chestnut!

    The cheapo lambda sensors on ebay are made in Poland (snigger) and the Bosch ones costing six times the price are made in.............. the very same factory in.............. Poland!!

    No surprise then, that when you lay a £10 sensor next to a "genuine" sensor costing £50 or more, the two sensors are, quite literally, identical..

    The car makers are notorious for fitting obscure, and patented electrical connectors to bog-standard lambda sensors.

    That is done quite cynically to force customers into buying a "genuine" replacement sensor with the same obscure, patented connector, at great expense, reaping huge profits for the car maker.

    Therein is the benefit of splicing a universal lambda sensor onto the existing electrical connector that was removed from the old and faulty sensor.
    Timing is usually handled by the ECU now so a strobe gun is useless
    Since this is a thread about MOT emission failures, we will be talking largely about older cars. Many of those cars will still be using a distributor-based ignition system.. and as such ignition timing is crucial to the efficient running of the engine. £10 for a strobe gun to check the ignition timing on those vehicles is peanuts compared to paying the labour charges of a garage.

    Since there is a common theme to your posts, I sense you've got something of an agenda here, anewman! You evidently don't like people doing DIY car maintenance. You want people to visit the garage, buy high cost "genuine" components, and pay a fortune to have them fitted!

    Fee Fi Fo Fum! I smell a wee vested interest in there. I think you are on the wrong forum!

    This is "moneysavingexpert.com".. And "moneysuckinggarage.com" is that way!
    >
  • anewmananewman Forumite
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    asbokid wrote: »
    Since this is a thread about MOT emission failures, we will be talking largely about older cars. Many of those cars will still be using a distributor-based ignition system.. and as such ignition timing is crucial to the efficient running of the engine.

    Even my 1994 Skoda Favorit has ECU controlled ignition timing advance with a Bosch Monomotronic system. All you have to do is turn the engine and line up the marks ensuring that the engine is at TDC with cylinder 1 on compression. The timing itself is not adjustable (either the rotor arm is in the correct position to be able to create the arc to the correct spark plug, or it isn't [both with and without the timing advanced]). A timing light is useless on such a setup. I don't know much about other cars of that age, but I wouldn't have thought a Skoda was more advanced than other cars such as Ford, Vauxhall etc.
    asbokid wrote: »
    I sense you've got something of an agenda here, anewman!

    You evidently don't like people doing DIY car maintenance. You want people to visit the garage, buy high cost "genuine" components, and pay a fortune to have them fitted!
    Quite the opposite. I'd hate to see anyone buy cheap and buy twice if they have a long-term interest in the car. If they just need a "get me through the MOT I'll get rid of the car in a year or two" then I'm sure the cheapies would be the best option. You can still buy genuine off ebay sometimes at cheaper prices.
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