Air/fuel Mixture For Emissions For Mot

[Tommer 0]

hi all,

 

getting ready to re-MOT my 1.9 GTI, I have the original 8v beauty!

 

I was advised that it failed on emissions last time but not buy a great number over the limit, and that I can asjust the air/fuel mixture to lower the emissions for the MOT.

 

can anyone offer some advice on this? I like where to start :S

 

cheers in advance.

 

tommer

[welshpug 1,627]

CO should be under 3.5%, ideally around 1.5%.

[kyepan 291]

You can adjust the mixture with the mixture screw on the AFM,

 

Not sure but adjusting the timing may also help to get a cleaner burn.

[Anthony 1,000]

What were the emissions results when it failed, as the solution will depend on whether it failed on CO or HC.

 

Limit is 3.5% CO and 1200ppm HC.

 

If it's failed on high CO (the usual reason) then normally you can turn the mixture screw on the AFM anti-clockwise a few turns to bring it down - aim for around 1-1.5% CO.

[Super Josh 4]

If it has only *just* failed the emissions, then an oil change usually brings it down by a little bit too

 

 

 

Josh

[richsmells 2]

If it has only *just* failed the emissions, then an oil change usually brings it down by a little bit too

 

 

 

Josh

 

Yup, I always change mine before MOT. Always way under the limit. Doesn't smell like it though!

[Tommer 0]

not sure what the exact failure was, will check when i get home and post the info up!

 

will also look at changing oil, any recommendations on brand and what ammount?

 

cheers again

 

tommer

[SurGie 54]

Have you tried cleaning the oxegen sensor ?

[welshpug 1,627]

Have you tried cleaning the oxegen sensor ?

 

 

 

 

no pug with an adjustable mixture has a lambda sensor

[SurGie 54]

Ok, when my 205 1.9 failed i cleaned up the sensor that goes into the water near where the thomostat is on top area of head, there is a wire attatched to it,

it passed it mot and i did nothing else. this is why i said try it.

[Baz 421]

The coolant temp. sensor then!

[SurGie 54]

Ok, when my 205 1.9 failed i cleaned up the sensor that goes into the water near where the thomostat is on top area of head, there is a wire attatched to it,

it passed it mot and i did nothing else. this is why i said try it.

 

 

I was told it the oxegen sensor by a mate, any way i gave it a clean and it passed. Not sure why though as it the coolant sensor like you said, anyway it was few years back

when i was not as wise with engines.

[Tommer 0]

MOT report thing says

 

Exhaust emissions carbon monoxide content excessive.

 

CO max limit 3.50% actual value 3.86% (Fail)

 

 

Do you think that the tank of fuel being half petrol hald redex might have helped make it fail?

 

 

also is this where I adjust the mixture? its an alan key head in there...

[lagonda 41]

Assume you're exaggerating re Redex content .... anyway, yes, I would think that any Redex in your petrol would harm your emissions read-out, although I would imagine more the HC than CO.

 

And, yes, that hexagon headed screw is the idle mixture adjustment.

 

Incidentally, when I took mine for MOT a year ago, just after engine rebuild, I had the ignition way advanced, so much so that I couldn't get the idle below 1500rpm. That was soon sorted, but now with an idle of around 950, I see the emission readings are higher (but still within pass).

 

So ... temporarily increasing your idle speed will probably get you through ... I think you're allowed up to 1800 rpm but best check, or try for 1500 as that passed mine at the time. I assume readings are better at higher idle as engine is running in a more efficient rev range.

[j_turnell 134 3 Cars]

Just give it a service and adjust the co using the 5mm allen key on the afm, anti clockwise to lean it off.

Edited September 27, 2008 by j_turnell