Weber on M10 - Failing emissions

[Dan!]

Hi all,

I replaced the standard carb on my '81 316 1.8 for a Weber 32/34 a few months ago. Car has sat about being tinkered with since then, had new leads, plugs, dizzy/rotor arm fitted, I have set up the carb the best as possible with the guide found on here, 2.5 turns in, adjust idle etc.

It now drives and idles spot on, but is reading ~8.2% CO on the emissions test.

Being my first venture into carburettor'd cars, I'm not sure where to turn next. Advice from my father includes, change the air filter, check jets are correct, check/adjust dizzy timing and get some hotter plugs.

Is there anything obvious we may have missed or anything which stands out as a more likely fix?

Any help in getting this sorted is much appreciated.

Dan.

[Peter V.]

First question:

* The weber is not modifed? Original setting in it?
* Did you connect the vacuumhoses to the distributor the right way? This because right timing is everything?

* The choke is comming of correctly?

[Dan!]

Weber was bought second hand, apparently off a running E30 318 M10, unsure of history other than that. I had to turn the mixture screw in a couple of turns and up the idle slightly to get it to run sweet. Choke is manual and you can have it fully off within a couple of minutes of the engine running.

I'm sure the vac hoses on the dizzy are correct, surely if they weren't it would run terribly? Which is what baffles me as it runs so well (I think!)

Is it worth loosening the dizzy and turning it slightly by hand and seeing if the idle/engine note sound any better/worse?

Thanks for the reply!

[Peter V.]

Ofcourse you can check the ignitiontiming.

Often an engine with a higher CO value runs very nice. Do you still have the possibility to turn in the mixture screw further?

It could be that the finetuning of the throtlevalve is a bit of?

[Reck]

I wrote that guide in the other section. Don't take it as gospel as they're all slightly different and have had the jets changed in many cases. Do what peter said and see if you can't be a little meaner with the mixture screw.

A garage with a Co2 probe would be best able to fix this though - shouldn't take more than a few minutes. They can adjust the two screws until you come within range of the allowed emissions. If it runs like crap at these settings you can always revert back to the others after you've got the MOT.

FYI I've just checked my previous MOT emissions readings (M10 1.8, Weber 32/34 DMTL) and here they are;

CO Max Limit 4.5% - Actual reading 0.76%
HC Max Limit 1200ppm - Actual reading 37ppm

So 8% definitely sounds high... !