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edhall · Joined: 03 Nov 2006 Posts: 5

Hi guys. As title says i've failed the MoT test on emissions - CO 8% instead of 4.5%.
I have yet to fiddle with the mixture but i have had a bit of a search and it would seems as if it's running on 'cold start' mixture all the time.
It starts okay hot or cold, though it always misfires when cold. It idles around 1000rpm but surges a bit.
So far i've swapped the warm up regulator but it doesn't seem much different to before (though i've not had it retested yet).
I can't see the air valve would have anything to do with it. Is there anything else i should look at? Anyone have an idea what could be wrong?
BTW it's a UK car so no cats, air valves or any emissions equipment.

Cheers, Ed

RonDwyer82-931 · Joined: 10 Sep 2007 Posts: 35 Location: San Leandro, Ca.

Leaky cold start valve?

Mike924 · Joined: 12 Aug 2004 Posts: 2601 Location: IoW UK

A common way of dealing with a duff WUR is to richen the mixture to be closer to the 'cold start' value all the time.

If your WUR was dead and you've now got a good one, you still need to crank the mixture down. Somewhere between 1/8 & 1/4 turn 'out' (anti-clockwise) on the 3 mm Allen adjuster screw on the air meter unit. That should at least get you through the MoT and then you can do the fine tweaking in your own time.

Was the replacemnt WUR new or a secondhand unit...?
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1985 Porsche 924 'Lux', Kalahari Beige (my ex)
1993 Porsche 968 Coupe, Midnight Blue, 6 spd

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