Mot failure on emissions.

[jdw66]

Long story. I fitted a new weber carburettor to my scirocco about 2 years ago. Somebody else tuned it and it passed the fast idle test (c02) with a reading of 3.4. Now last year i noticed the diaphragm was bent on the carb so i bent it back to it's correct position. Now the carb was tuned with the diaphragm bent ( we didn't notice at the time) so when adjusted it i upset the carb set up, plus there was a split in a vacuum pipe, so the car took about 5 attempts and 15 minutes to get throughout the fast idle test. So today was MOT day and i anticipated problems with the co2 test, and christ i wasn't dissapointed. Got a reading of 8.7. Mot guy reckons it was down to a new exhaust back box and down pipe i fitted 2 days ago. So the question is how am i going to give the emissions down.

[mark1gls]

Screw in the mixture adjustment screw on the carb, mines on the side but I have a slightly different carb as I have a Mk1.
Make a note/picture of where is is now and screw it in, you may need to also adjust the idle speed, there's another screw for that. Basic set up for a Webber carb is screw mixture screw all the way in the unscrew 1 to 2 turns.

You are best to get the garage to set the mixture as they car hook it up to a CO machine and get the right reading.
More info here.

http://www.carburetion.com/Weber/adjust.htm

[jdw66]

Thanks for the advice. Hopefully it will work but 8.7 to 3.5 is one hell of a drop just by tuning the carburettor. I think something else is involved. IE: a vacum pipe. Finding it hard to accept that changing 2 exhaust sections would affect the reading. Think i might have to get the garage to have a look at it. Unfortunately i'm skint at the moment and i use the car everyday, at least i used to.

[mark1gls]

How old is your air filter, old dirty air filters increase emissions as not so much air can get in. If you still use a paper filter and it's over 12 months old buy a new one.
Have a look at it check the condition of it even if it's only a few months old in case it's contained with oil if problem with the engine breathing.

You can reduce the emissions that much by turning the screw on the Webber as when I got my Mk1 on the road for the 1st time in 10 years the emissions was sky high like yours and the garage doing the MOT adjusted the carb so it would pass.

[jdw66]

There's a k and n in there at the moment, about a year old . I've had a lot of trouble with the oil emulsifying this winter first time ever in 10 years. And it's been getting everywhere. In fact it's been so bad bad i thought the head gasket had gone. Did a compression test and every things fine. Coincidently it's the first time i've used a quality oil. So the filter is very likely to be contaminated. Will shove in cheap one when the car goes for it's next attempt at the mot. Thanks for the advice, John.

[james butler]

I've had a lot of trouble with the oil emulsifying this winter first time ever in 10 years. And it's been getting everywhere. In fact it's been so bad bad i thought the head gasket had gone. Did a compression test and every things fine. .

the fact you say its never happened before should ring alarm bells.
a compression test will not tell you if water is getting into the oil and vice versa, the only way to do that is to pressurize the water system and see if it holds over time.
the weber is a simple carb and will be down to mixture either effected by air leaks or something mechanical not quite set up right.
whoever set it up the first time shouldn't have set the Co so high, my last MOT was 0.8% and had to richen the mix so it wasn't running so lean.
exhaust has a big part to play as my old jetex exhaust was naff and made emissions worse, what type of exhaust have you fitted?
i had a stainless custom exhaust fitted last year and it knocked 2% Co straight off my emissions from last year hence my readings of 0.8%

[jdw66]

I was lying in bed last thinking it could be the head gasket. As i said compressions fine, she's not losing water or power but that amount of mayonnaise is a worrying factor. And i assume a car with a dodgy head gasket would send the emissions sky high, and stupidly i've been running around without the temperature gauge working so it could be the gasket even thought my fantastic mechanic who set the carb says no. He thinks it's down to condensation and short journeys. The exact same circumstances as the pervious 9 years without the mayo.
As to the exhaust the down pipe was from the local motor factors £50 and back box was from vw heritage . Not sure of the makes without getting under the car. One thing i do is the quality is not great especially the down pipe .

[mark1gls]

Where is the Mayo, oil filler cap or in the expansion tank?

I did read on the Mk1 golf forum about putting a latex glove on the expansion tank (cap removed) and start the car if the glove inflates in the first minute you have a head gasket problem. The glove will inflate if you leave it on for a few minutes as it's pressurised coolant system so don't worry if you leave it longer and it does inflate that's normal.

[jdw66]

Dipstick is covered in it, as is the oil cap, breather pipe (totally clogged) on filter housing and fair bit under the rocker cover when i changed the gasket last week. Everting has been cleaned out.
Glove idea sound brilliant will give it a go as soon as i get the chance. Many thanks , john.

[mark1gls]

More info here.
https://vwgolfmk1.org.uk/forum/index.ph ... e-a-kettle

[jdw66]

Thanks mark1gls,will check it out.