Technical Just Failed MOT on Emissions "just" .. help needed.

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Technical Just Failed MOT on Emissions "just" .. help needed.

Re: failed MOT because of emissions!

The actual recorded figures are a great help to pin down the fault and eliminate others so always get them and put them in your posts

But if, say, the CO reading is way above 0.3 for 1st and 2nd idle test then, assuming air filter and sparks to be in good shape, the first step would be check out the pre cat O2 sensor. This leans off the fuel when the engine is in steady rpm -like idling or any steady speed state- so without that it'll be guessing and over fuelling in a big way. A sudden noticeable drop in fuel economy would also be a clue


thanks for the reply :)

i have checked the reading and eveything but the CO is correct. the CO reading is 1.67 and thats really really high! i have noticed a drop in fuel economy but i just thought it was me getting less for my money at the petrol station :p

what can i expect it to be if the CO is that high?? :(
 
Re: failed MOT because of emissions!

Same advice as before

If the CO reading is way above 0.3 for 1st and 2nd idle test then, assuming air filter and sparks to be in good shape, the first step would be check out the pre cat O2 sensor. This leans off the fuel when the engine is in steady rpm -like idling or any steady speed state- so without that it'll be guessing and over fuelling in a big way. A sudden noticeable drop in fuel economy would also be a clue

What engine size is it?

Do you have a voltmeter/ohmmeter?

Do you have some acupuncture needles or similar?

If so you can check out a pre cat O2 sensor quite easily without removing it.

Still better to post ALL the actual emissions figures as they can, for instance, be a "pass" but so abnormally low that it gives a good clue as to what actually needs attention.
 
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Re: failed MOT because of emissions!

thanks for all your help :) i will add the readings as soon as i can. a quick question, would a badly fitted exhaust cause the emissions to rise like they have?

thanks :)
 
Re: failed MOT because of emissions!

Depends what you mean by "Badly fitted" If it's a leaking exhaust then it will throw things out for sure but I'd hope an MOT tester would have spotted and reported a leaking exhaust though if it's bad enough. After all it's likely to make you and your passengers pass out so it's pretty high on the MOT testers fail list

High CO will usually indicate an over rich mixture of unburnt fuel in the exhaust

I'd check the voltage outputs on the pre cat O2 sensor
 
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Re: failed MOT because of emissions!

After all it's likely to make you and your passengers pass out

Well.. you get a killer headache about 10 min before you pass out :ROFLMAO:
So.. if all of a sudden you get a severe headache while in the car :eek: it is a good idea to take a break and get out for a bit.. if your headache goes … ave a close look at the exhaust manifold (saved me life this.. :eek:)
 
Re: failed MOT because of emissions!

I agree, CO Carbon Monoxide gives me a howler of headache. A lot of people just fall asleep (probably with a headache, wondering what it is) and it's killed a lot of holidaymakers in holiday flats and villas where a gas appliance has a poor or blocked exhaust duct combined with poor ventilation.
 
Re: failed MOT because of emissions!

i pretty much did what you guys told me to, thanks for the help but it turns out that it is my Cat which will need replacing :'(

what a pain!
 
Re: failed MOT because of emissions!

You still haven't posted all your emissions figures but i would expect high HC as well as high CO if cat had gone. Would like to see your pre cat lambda readouts and see if your engine is going into closed loop
 
Re: failed MOT because of emissions!

i pretty much did what you guys told me to, thanks for the help but it turns out that it is my Cat which will need replacing :'(

what a pain!

Ask for proof of comittment, you dont want them coming to you having fitted a new cat saying "sorry mate its still the same..." If it dont fix it you shouldnt pay...
 
Re: failed MOT because of emissions!

I have something similar for my 51 1.6 petrol multi.

CO Emissions are 0.5 for both fast idles and 0.52 for normal idle (limits 0.3, 0.3, 0.5). MOT garage report hearing 'blowing' from front of exhaust and having removed heatshield have found a small crack in the exhaust manifold which they claim will be throwing out the exhaust settings. New manifold from fiat (deale ronly part) is 165+vat. The exhaust blowing was not audible (from in the car anyway)

Anyone think the manifold really needs changing or that I should try the other fixes (air filter, oil change, fuel/cat cleaner) - garage claims air filter will make no difference? Have tried to source a second hand exhaust manifold but they all seem to be cracked already making me think most people are driving them around with the crack.

Car had an MOT and service a year ago and has only done 2k miles since (most recently a couple of longer journeys) but no more recent servicing - thoughts?
 
Re: failed MOT because of emissions!

Always post ALL the emissions figures as even though they may be in the acceptable range they give clues to the problem area otherwise there's v lu ble p rts of the inf rm t n m ss ng and it b c mes p re gu s w rk:)

Could have your exhaust manifold weld repaired

http://www.muggyweld.com/silvercast.html
Nice vid. Filled holes but no porn
 
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