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Failed MOT

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Hi Chaps

sorry wasn't sure where to place this post.

so today my car went for a mot for the first time in 5 years' unfortunately it failed  Description: Description:

so the issues were high c02 which came up at 9.99% apparently the limit is 2.5 judging from my emission results and if I'm honest I knew it was running rich as I can smell it if that makes sense or tell me I'm talking sh**  Description: Description: Description:

the second thing was brakes imbalanced across the rear axle by more than 50%. the technician said the driver's side rear brake was non-existent.

The rear brake shoes on both sides were changed and passenger side brake cylinder also, ive just picked up a new cylinder and will fit that the weekend but wondered if I need to do more’ would it be the cylinder ??

Back to the emission’s any ideas guys I haven’t a clue what to do hear’ will it be a carb adjustment ??

Really appreciate your help here guys as I’m lost now
 

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Prob not ideal to have changed just one rear cylinder. They are almost consumables either seizing solid or leaking fluid and ruining the shoes in the process. If you are lucky its seized…..

Another trick is to use a bradawl or pointy screwdriver to pull down the wedge adjuster thru a bolt hole with the wheel on and off the ground. This takes up all the slack so half the pedal stroke isn't wasted doing nothing

You don't say if GTI or carbie but assuming plugs, air filter, oil etc are pretty new both really need a CO meter and someone who knows what they are doing, its really easy on both to foul up twiddling random adjustments .    

1983 Mars Red 1.8 Golf GTI
1987 Alpine White 1.8 Clipper Cabriolet

The trouble with doing nothing is that you never know when you are finished.

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You're guessing on the CO emissions unless you have a gas analyser or lambda probe of some kind. Do you know what the HC was too?

There's ways to sense whether its running rich or lean if its K-Jet, from experience.

If its a carb car…..what carb is on it and what engine? I am guessing 1800 from the pic.

Regarding the brakes, it will probably be something obvious if its completely not working on one side - could be a kinked brake line, for example. Or the mechanism seized in the drum. Its obviously worth having new drums (they're only about £10???) or taking the lip off and cleaning up the old ones, then you can do the lion's share of the adjustment with the drum off, then put it on and complete the adjustment, which is awkward because the auto-adjusters never seem to work.

                                

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Thanks guys the reason one cylinder was  changed was the dummys at euro gave me one wrong so changed just the one, sorry forgot to mention its a 1.8 petrol auto with a  Webber carb

HC max 1200ppm actual 475 ppm
CO max 3.5% actual 9.99%

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Forgot to mention guys' it had an oil change and filter change

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Old or blocked air filter will increase emissions.

Could be the Webber carb needs adjusting, the mixture screw is on the side of the carb and needs screwing in a little, I guess it's not a garage you usually use for an MOT as my local garage adjusted mine for me when my car as over the limit as it takes seconds to adjust it and while it's on the machine it's the perfect time…

1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 317,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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Rear wheel brake cylinder… there is 2 types, 1 for cars with the brake pressure reduction valves fitted which yours should have looking at the picture, the valve sits underneath the master cylinder. 1 type with out the valve.

You need the bigger rear wheel cylinder.

Pics of valves here..
https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=technical%2Frunning-gear_2%2Frear-brake-regulator

1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 317,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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Thats Guys especially mark1gls

The air filter is new so guess the carb needs adjusting, would there be any guides for this anywhere ?

Ive picked up a rear wheel cylinder from car spares and stated the registration, its the same as the one that needs removing so fingers crossed, think i will do a full brake clean down , I'm not even sure how i would search for the webber carb is there a specific name for it ?

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quote="okmate


HC max 1200ppm actual 475 ppm
CO max 3.5% actual 9.99%
quote]

I think its generally as the co gets worse the hc  gets better,  hence the low reading

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Webber carb set up instructions.

https://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=helllllpppp%2Fweber-fitting-guide

You will find as you adjust the mixture the idle speed will change so you also need to adjust the tick over.

You only need to move the mixture screw a little to make a difference.

This is assuming the engine timing is spot on.

Last edit: by mark1gls


1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 317,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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thanks pal,

Ive just sourced Rubjohhy pdf from his signiture, it would seem rule of thumb looking at the other information collated is turner the jet in decreases the Co2 but i must try and maintain tick over

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Firstly….its CO, not CO2!!!! But I know what you mean.

Without a meter or gas analyser of any kind, the technique is approximately this:

Turn the mixture screw anticlockwise (out, increase fuel, increase CO, reduce AFR) until the revs start going down. Then turn it clockwise (in, decrease fuel, decrease CO, increase AFR) until the revs decrease again. Then turn it back a tweak so the revs increase.

Revs will vary but should be approx around the idle range. If its wildly low or high, or the car can't run and stalls during the above procedure, adjust them then do it all again.

This assumes the carb is jetted correctly for the application. That's a whole another thing!!

                                

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paul_c said

Firstly….its CO, not CO2!!!! But I know what you mean.

Without a meter or gas analyser of any kind, the technique is approximately this:

Turn the mixture screw anticlockwise (out, increase fuel, increase CO, reduce AFR) until the revs start going down. Then turn it clockwise (in, decrease fuel, decrease CO, increase AFR) until the revs decrease again. Then turn it back a tweak so the revs increase.

Revs will vary but should be approx around the idle range. If its wildly low or high, or the car can't run and stalls during the above procedure, adjust them then do it all again.

This assumes the carb is jetted correctly for the application. That's a whole another thing!!

Thanks Paul C  will i have to adjust the idle first ? i been at the moment it idles perfect and starts first time

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It depends if it stalls during the sweeping of the mixture to find the ends (lean misfire limit and rich misfire limit).

You'll need to set the idle speed afterwards, for sure, but its very very easy on a Weber carb and can be done with no tools, unless yours is weirdly different???

                                

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Sorry for all the questions,

Is it worth  starting at baseline levels first as the webber PDF states, I'm not sure it was ever setup properly judging by the number of things that were bad on the car.
also can the adjustment be made without the air filter on ?
Attachment
weberbasesetup.pdf

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You need to have the air filter and air box on the car when adjusting the carb or there will be to much air getting into the carb.

1988 Mk1 Golf GTi Cabriolet 1.8cc DX, K-jet. Daily drive. 317,000 miles and counting
1978 Mk1 Scirocco GLS 1.6cc FR, Webber carb. Weekend toy.

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Just wanted to double check< do you think its best if i start with the baseline settings ?">

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You can use a Gunson Colortune.
I a "see through" spark plug.
Adjust the co screws until the flame is pale blue.
Job done.

bougie.jpg

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Hi Chaps

I've had a go today and feel pretty chuffed, the mixture has been set' it was really far out to be honest so I'm hopeful now' I took it for a spin and she drove lovely really responsive and smooth.

The rear brakes have also been done there was grease on the shoes so a quick cylinder change and good clean before bleeding, My only issue is the back brake is now operating on 1 click when driving down the road the back wheels lock up as soon as i pull the handbrake up .

Question is ….Is 1 click ok or should i realize the cables from the handbrake until i get 2 ?

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Failed MOT

I always go for 3 clicks. I would slacken of your hand brake cables fully before adjusting the shoes and then you can continue to adjust on the cable as they wear until you next take the drums off


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