polo failed mot on high H.C. - rustbucket
Just got the message from my daughter that her k plate polo has just failed the mot on high hydro carbon reading, until she returns with the print out i do not know what the other readings are.Last year the hc reading was higher and the co2 was higher than the previous year and the lamda was about the same and passed ok.So it seems it might be a progresive problem.Without throwing lots of money at it immediately can annyone give a clue as the reason ie weak or rich mixture that may be the problem here?

thanks
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rustbucket (the original)
polo failed mot on high H.C. - rustbucket
update to emmision figures at fast idle, passes ok at idle

last year
co2 .16 pass
hc132 pass
lambda 1.02 pass

this year

co2 .54 fail
hc 216 fail
lamda 1.03 fail


any ideas please before I change parts Unecessarily

polo failed mot on high H.C. - Andrew Moorey (Tune-Up)
Thats CO not CO2. Its only just out of spec and my initial reaction is that the catalytic converter hasn't 'fired up'. What kind of motoring does the car get, when was the oil last changed and where does your daughter buy her fuel??
When the MOT was carried out what kind of distance was travelled prior to the test and was it tested immediately or allowed to sit around cooling its heels for a few hours?
Sorry for so many questions but it all builds a picture.
Andrew

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polo failed mot on high H.C. - John S
Rustbucket

The oddity is that, according to my last MOT, to get a pass on lambda it has to be 0.97 to 1.03 . So, 1.03 is actually a pass, not a fail. The figures certainly show the cat is working and I reckon Andrew is right.

JS
polo failed mot on high H.C. - John S
Oh, another thought. It passes at idle but not at 3000 rev/min? Not as simple as a blocked air filter is it? That would certainly have more effect at the higher engine speed.

JS
polo failed mot on high H.C. - rustbucket
Thats CO not CO2. Its only just out of spec and
my initial reaction is that the catalytic converter hasn't 'fired up'.
What kind of motoring does the car get, when was the
oil last changed and where does your daughter buy her fuel??
When the MOT was carried out what kind of distance was
travelled prior to the test and was it tested immediately or
allowed to sit around cooling its heels for a few hours?
Sorry for so many questions but it all builds a picture.
Andrew
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Simplicate and add lightness!!

Thanks for the reply
answer to questions

short journeys ie 4 mile to work and 4 miles return each day and a 30 mile trip round the m25 every week in the evening when the traffic is moving.

last fuel from sainsburys and total

about 2 to 3 miles to test

test done immediately and test repeated to allow engine to get hotter after first test failed, on second test lambda reading was 1.02.the co was slightly higher with hc slightly higher

yes 1.03 is a pass, just got carried away with typing fail.







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rustbucket (the original)
polo failed mot on high H.C. - Roberson
Its always best to check the cheapest and easiest items first. In this, Spark plugs and air filter would be a start.
polo failed mot on high H.C. - jc
Also with a lot of short journeys petrol gets into the oil;either get the engine well hot(Essex or Italian tune-up) or change the oil.
polo failed mot on high H.C. - Andrew Moorey (Tune-Up)
My suggestion would be to change the oil and filter, use quality oil, something with a 'name', fit a new air filter and take the car for a 'brisk' run of 10-15 miles and get the test done immediately. INSIST the oil temp is measured (most mot stations seem to bypass this) to be doubly sure the engine is hot enough and with luck she will squeeze through. As the car is used predominantly for short journeys I'd recommend using a fuel such as Texaco which has a very high detergent element to keep the engine clean.
Let us know how you get on!
Andrew
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polo failed mot on high H.C. - rustbucket
Thanks for the advice Andrew

will report back after the retest

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rustbucket (the original)
polo failed mot on high H.C. - Chris S
My suggestion would be to change the oil and filter, use
quality oil,

Just out of interest, how does changing the oil and filter affect the emissions?
polo failed mot on high H.C. - Roberson
The filter doesn't have any effect on emissions, its the oil.

During short journeys, where your engine (and more so) your oil doesn't reach operating temperature, you'll suffer from oil dilution by petrol (amongst other things). When the engine is running, the vapors from this will be drawn into the induction system by the crankcase ventilation system (breather pipes) and be burned off. The more dilution there is, the more vapors there are to be burned off.

If you haven?t got time to change the oil before your test, a long drive on fast roads will usually burn the petrol off.
polo failed mot on high H.C. - Victorbox
Andrew, I noticed when my wife's car had its first MOT recently the print out said oil temperature test bypassed. How should they measure the oil temperature - with some probe presumably?
polo failed mot on high H.C. - pmh
I have seen the oil probe heated up with a cigarette lighter to allow the test to proceed without warming up the car!!!!


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pmh (was peter)


polo failed mot on high H.C. - John S
Yes, normally measured with a probe. As I understand it, these days they do a 'quick' emissions test first, without checking oil temp. If the car passes without checking the oil temp then thats fine. if it doesn't they go further.

JS
polo failed mot on high H.C. - rustbucket
My suggestion would be to change the oil and filter, use
quality oil, something with a 'name', fit a new air filter
and take the car for a 'brisk' run of 10-15 miles
and get the test done immediately. INSIST the oil temp is
measured (most mot stations seem to bypass this) to be doubly
sure the engine is hot enough and with luck she will
squeeze through. As the car is used predominantly for short journeys
I'd recommend using a fuel such as Texaco which has a
very high detergent element to keep the engine clean.
Let us know how you get on!
Andrew
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Simplicate and add lightness!!

Update to polo mot fail. changed oil +filter ,air filter, replaced spark plugs and lambda probe as when inspected was sooty and partly obstructed in the vent slots and had done 71000 miles gave it a good run, passed ok.
the emission figures are :
co .o3
hc 32
lambda 1.01
idle co .02

figures before and failed:
co .54
hc216
lambda 1.03
idle co .33
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rustbucket (the original)
polo failed mot on high H.C. - Andrew Moorey (Tune-Up)
Thanks for the feedback, pleased it passed. Shows how much the old fumy oil pushes up the hydrocarbon levels!
Andrew
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Simplicate and add lightness!!
 

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