M.O.T. Failure on emissions. advice please

[davidm]

Hi all,
My van is a 1985 petrol 1.9 DG. It has just failed on CO level being too high at 5.58%, (max. for pass is 4.5%). My first thought is it's probably something to do with the carb. which was overhauled last year by local mechanic, not particularly experienced with pierburg 2e3 carb,- needle valve kit fitted. I think this is only significant change since previous mot. I am wondering if it is possible to adjust mixture or whatever to a point where i should expect it to get it through re-test, without actually having it on gas analyser, or possibly while it is being re-tested if the tester will allow it. As i know carb settings were messed about with a lot last year during holiday breakdowns!, by myself, one garage and one breakdown mechanic (who admitted he was a diesel truck mechanic), am i barking up the right tree or is it more likely to be something else? Air filter, plugs, oil, oi lfilter were changed last year shortly before taking it off the road for winter. Or should i just cough up and book it in to any garage with diagnostics and let them try to sort it, OR indeed a local VW garage, to make sure timing and carb are set up right.
THANKYOU in advance for help.
David

[Ian Hulley]

I'm sure someone will know the base/default carb settings ... I've never adjusted mine so couldn't tell you. Sounds to me like it just needs taking back to 'standard'.

Ian.

[Red Westie]

You are quite right, the mixture screw needs screwing in 1/3rd to half a turn. Adjustment can be done well enough by ear: screw in slowly until the engine starts missing (there will be a very subtle change in engine tone) when you reach this point back off screw 1/4 turn until running smooth again. Set! all of two minutes work (hot engine imediately after a run, don't let it idle for too long, 4-5 mins max)
What is anoying is the fact that idle CO is a pretty meaningless figure anyway in terms of pollution (unless you are stood for hours in traffic) and as soon as the engine comes off idle the carburrettor runs on a completely different jet with different emmisions. But hayho, if thats what they want.
Martin

[Mushr00m]

Failing it being what Red Westie has said, you could do worse than changing the engine oil, oil filter & air filter.

Best of luck.

[toomanytoys]

check air filter in case something has nested in there...
and as redwesty says.. 1/3rd of a turn... 1/2 turn might bring it nicely down..

I hate it when I hear things like "several people have adjusted it" it usually means they have buggered it up....

[davidm]

Thankyou very much for the replies.
I had checked air filter and, as i said, plugs oil, oil filter, air filter and leads were recently changed (in mileage terms). I will give the CO adjustment, as described by redwestie, a go and take it back. I have read on the forum here that one should give it a good blast up the bypass (ooh er mrs!) just before "presenting it" for test. I intend to find out how amenable the tester is about me making adjustments during the test. Are they allowed to do that? Is there anything else that might help on the day?
The only other info on analysis sheet was HC level 187ppm, in case thats relevant.
Cheers, David

[Aidan]

wrap some gaffer tape round the big rubber vac pipe coming off the manifold that is the vacuum take off for the brake servo - the pipe is reinforced with steel and rusts and becomes porous, even tho co good hc high cos 3 and 4 are running lean with air being drawn in through the porous pipe - spray it with fuel substitute revs rise same check as for any inlet leak

had this myself once upon a time and someone recently reflagged this problem

[davidm]

just to update,

I adjusted mixture as described by red westie, took it for a run, back to mot centre, and it passed !
Fortunately the guys there were not busy this afternoon and were very helpful. the co level had gone right down, but hydrocarbons had gone up around limit. Another small adjustment and they passed it. They also put some black insulation tape on headlamps to pass the only other thing it had failed on. The test centre was JUST MOT'S in Tonbridge, so i would recommend them. Last year, they took a tail-light bulb out ,on the retest , and cleaned the connnection to get it through. Thats what i call good customer service ( and common sense) and why i will be going back. Also, they are currently only charging £25 with a free re-test within 10 working days. (I sound like an advert)
So that saved me £43+ vat that John Bowles volkswagen garage quoted for adjusting the carb, on the gas analyser.

Thanks again for help,
David

[Rozzo]

just to update,

I adjusted mixture as described by red westie, took it for a run, back to mot centre, and it passed !
Fortunately the guys there were not busy this afternoon and were very helpful. the co level had gone right down, but hydrocarbons had gone up around limit. Another small adjustment and they passed it. They also put some black insulation tape on headlamps to pass the only other thing it had failed on. The test centre was JUST MOT'S in Tonbridge, so i would recommend them. Last year, they took a tail-light bulb out ,on the retest , and cleaned the connnection to get it through. Thats what i call good customer service ( and common sense) and why i will be going back. Also, they are currently only charging £25 with a free re-test within 10 working days. (I sound like an advert)
So that saved me £43+ vat that John Bowles volkswagen garage quoted for adjusting the carb, on the gas analyser.

Thanks again for help,
David

sorry but i disagree, good service would have been to adjust the mixture screw(schoolboy mechanical knowledge needed) on the first test and stick some tape on the lhd lights. oh and don't think it hasn't cost you owt,, its cost the price of fuel to drive there and back,, the time off work and the worry surrounding a fail bloody jobsworths the lot of em

[Pepperami]

In the olden days when i had one of those 1.9dg things in the back my mot tester done all of the adjusting of the carb for me to get it through the mot. Spose that's country living for ya

[davidm]

Rozzo,
I guess you are right, they could have done it the first time round but I am just glad to get it through with very little expense. How many places do you know doing MOTs for £25, a free re-test and a bit of help to pass it? My previous experience (25 years of taking cars for mot) is to find testers who dont care, dont have any common sense and are not willing to do any thing to help their customers, or are looking for small things that dont need doing so they can charge you to do it, or charge for re-test if you take it away, etc, etc. Maybe i've been going to the wrong places.

Pepperami, That WAS the old days, in most places. should be that way now, but hey ho.

[Rozzo]

congrats on getting it through tho

[mikec]

Can we just confirm the "Mixture screw is the "CO Adjustment Screw" on the bottom right? Please?

[davidm]

Mikec,
I am not sure if you are informing for clarification or asking. Anyway the answer is yes, i think.