MOT emission fail dilemma

[Darkhorse]

Took me 1.9 WBX petrol in for the MOT last week and failed on a 4.58 CO reading (HC passed at 253ppm) I know the carb 2E3 needs a rebuild and the choke pull down is pretty much shot (I've a rebuild kit and a new pull down unit ready to go) and 8 days to get back for the MOT retest. I've not done a carb rebuild before, but think with the good info on the wiki pages and the right tools I should be able to manage it.

My challenge is that we're off to Glastonbury in the van tomorrow and ive been warned off doing anything remotely disabling until we get back - the day before the MOT retest, so will not get the rebuild done beforehand.

I'm hoping a good run up the M5, a bottle of fuel additive, a new air filter (or removed?) or a tweak of the fuel / air mix. Am I right in thinking high CO reading is a result of too rich a mixture?

I also read some where but can no longer find that it might benefit if I bypass the crankcase emissions?

Any other tips much appreciated. Cheers

[itchyfeet]

They only test co at idle afaik and there is an adjustment screw you can use.

Your van is now illegal to drive other than to a retest

[kevtherev]

I wouldn't start twiddling mixture screws without a gas analyser.
I am surprised the motter hasn't offered the service.

[itchyfeet]

[itchyfeet]

I wouldn't start twiddling mixture screws without a gas analyser.
I am surprised the motter hasn't offered the service.

Agreed, I have a gunson gas tester they are about 100 quid or ask the MOT station if they will adjust it for you before the test.
Maybe he is doesn't know how on this carb

[CJH]

In the absence of a gas analyser you can get close 'by ear'. First of all, get the engine warmed up and idling properly, then, with the engine off, count the number of turns it takes to wind the idle mixture screw all the way in (so you can get back to where it is now if you get in a muddle). Then wind it back to that point, and with the engine running, wind it in gradually until the revs start to drop. Then wind it out half a turn. You want it on the minimum setting that lets it idle cleanly.

[djaychela]

They only test co at idle afaik and there is an adjustment screw you can use.

Your van is now illegal to drive other than to a retest

Depends what you mean by "illegal".

[Shaundon]

pulling off the rubber hose from the breather tower to the carb might just get you through (just dont tell anyone youve done this and replace it as soon as you leave the mot station)

Not a good long term solution but if your in a tight spot and want it to pass today. Also ask them to rev it up a bit just before taking the reading.
Also you can turn in the idle mixture screw as described above if the above doesn't work.

[itchyfeet]

They only test co at idle afaik and there is an adjustment screw you can use.

Your van is now illegal to drive other than to a retest

Depends what you mean by "illegal".

Onnce it's failed an MOT you don't have an MOT even if you put it in a month early.

No MOT means it's not legal to drive on the road, your insurance may be invalid ( although it's not safety related so possibly not deemed important by an ombudsman)

They don't give out fines for driving legally and there is a fine for driving with no MOT

[Darkhorse]

Yep, bit of an odd setup with the garage and MOT. The garage specialises in VWS and you can book in for an MOT through them, but they then cart off the vehicles to a separate MOT test garage that does - just MOTs. The VW garage was too busy to take in for the MOT suggested I go round to the MOT garage directly. So I did, said it was on the instruction of the VW garage and got the fail. Plus charged an extra £5 for going independently!

Might as well give something a try prior to the retest. Then I think I'll look for another place to throw my hard earned at.

Thanks again for the helpful info.

[Darkhorse]

In the absence of a gas analyser you can get close 'by ear'. First of all, get the engine warmed up and idling properly, then, with the engine off, count the number of turns it takes to wind the idle mixture screw all the way in (so you can get back to where it is now if you get in a muddle). Then wind it back to that point, and with the engine running, wind it in gradually until the revs start to drop. Then wind it out half a turn. You want it on the minimum setting that lets it idle cleanly.

Thanks. Good plan. It's a standard thread I.e clockwise to turn all way in?

[djaychela]

Onnce it's failed an MOT you don't have an MOT even if you put it in a month early.

This isn't true. I asked VOSA previously about this (lengthy debate on a rally forum about it, with opinions on both sides), and they confirmed that failure of a test doesn't invalidate the current MOT.
However, you are liable to be prosecuted for any issue on the vehicle that contravenes C&U regulations. Clearly for something like bald tyres this would be a: likely and b: dangerous. For something like an idle emissions issue, I'd think the chances of even being detected are vanishingly small, and would usually lead to needing to take an MOT.

.. your insurance may be invalid ( although it's not safety related so possibly not deemed important by an ombudsman)

Generally not true as well, unless specified in the policy.

[Darkhorse]

^^^
I did try and tax the vehicle online earlier today and got blown out 'no valid mot'. On paper, both tax and mot expire June 30. Oddly the gov website failed to mention when I'd get a road tax refund for those days that have been stripped away

[marlinowner]

That's probably because there won't be a valid mot for the tax start date ie July 1st. When an MOT is issued after a fail and retest, it is still dated to the expiry of the previous MOT, which would imply that previous one is still valid.
Confusion arises because to use a vehicle on the road (once three years old) it has to have a valid MOT and also be roadworthy. The question is whether failing the MOT means it is unroadworthy - but if that is the case then it would be an offence to drive it under any circumstances, including to and from the MOT station, so I think most likely that it is ok to drive until expiry of previous MOT unless fail certificate says vehicle is in a dangerous condition. (IMHO)

[itchyfeet]

Thats news to me but the thing is even if some bloke as VOSA says it's OK what if plod has it on his ANPR that you have failed an MOT, Plod might not be an expert in safety or understand the fail details so pulls you for it on the way to Glasto, better not have any of those herbal cigarettes and you may be late for Glaso or not get there at all.