Club 80-90 Forums

CO is just one part of the exhaust gas composition.
What is everything else doing?

lambda/AFR?
CO2?
O2?
HC's?

Setting the CO is a load of "Balls", you need to see the whole picture to see whats really going on.

Them crappy little CO meters cause more trouble than they fix, the amount of times I've had vans in where someone has been "fixing" it is unreal, they manage to get the CO to the volume that the "manual" says, but all the other gasses are a mile off.
Setting the mixture is a comprimise, making the best of what you have to work with, getting them all as good as you can get, watching each one individually and watching the composition as a whole.
I suspect if it's running at below .1% you have a massive leak in the exhaust or a massive vacuum leak, check manifolds, vacuum pipe (favorite) pipes off, vac advance diaphragm split.
how have you set the timing?

VWCamperfan wrote:I would be tempted to check your meter, even with the mixture at very lean I would be surprised to find the readings that low because you should always have some CO output higher than you are getting.
Do the readings change when the engine is just started and the choke is closed or you restrict the airflow?
Have you got the air filter and associated pipework connected when taking reading as this would affect the emissions too?

Its an MOT machine im using, last calibrated a few months ago so readings will be spot on.

An air leak is unlikely, i have fitted the carb and manifold with all new gaskets and dont get any improvement when covering the joins in grease...

Im thinking i need a new carb!! Cheers tho people...

So what are the rest of the readings then?

you need to record all the readings as simon has already said, you also need to check the readings at a fast idle as carbs have 2 circuits you may have a lean mixture at idle but be spot on at 3500 rpm. then you are just looking at the idle circuit fault. if you have an air leak then o2 will be high ie 3.0 +.

also lambda / afr on the gas machine is an important factor and will indicate where the engine is happy to run.

get the fast and slow readings up so we can have a look.

I will print off full results on monday but from what i can rememeber HC is about 200-300PPM and lambda was about 1.25ish...

will put full results up soon

VWCamperfan wrote:The limit for CO emissions is 4.5%. If yours is at 0.10% then thats way below the limit and I would be a happy as a pig in poo!
How come you want to change the carb etc. when it would sail through an emissions test?

My test sheet (from friday) says the limit is max 3.5% CO? Has it changed, or do different garages have different standards or something? The bit of paper does specifically say "Non-catalyst equipped vehicle".

My DJ returned a result of 1.927% CO and 103ppm HC (Max. 1200ppm).