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PostPosted: Wed Aug 21, 2019 9:49 am 
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Joined: Mon Nov 21, 2011 12:23 pm
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Location: London & Suffolk
Car Model: Saab 99 Turbo
Hello all, my '80 Saab 99 single carb is at the local garage for it's first (and last?) MOT and the chaps are struggling to get the emissions down to a 'Pass' level. Are they missing something obvious I could point them to? I want to get this on the road and a few miles on the clock before attempting a run down to the GoodWood Revival in September... Failing that, who out there has a replacement carb in good/new condition they are willing to part with? Peter

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PostPosted: Wed Aug 21, 2019 10:42 am 
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Joined: Wed May 12, 2004 9:46 pm
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Location: Mulbarton,Norfolk
Car Model: TTid's only now :-(
I con't remember the correct spec, but about 3% was what I thought it should be running at.

Being a carb, they could just screw the needle down to get a pass reading, and reset it back for decent running afterwards...

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PostPosted: Wed Aug 21, 2019 11:44 am 
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Joined: Mon Feb 19, 2007 2:17 pm
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Location: Kent
Strombergs I've had have worked OK so I've not had to work on them. In the short, narrow "box" on the side of the carb is a bi-metal strip type compensator to keep the mixture constant. This might be the cause of your problem. Google it for explanations and possible cleanout and adjust. Notes on it should be in any manual you have.


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PostPosted: Wed Aug 21, 2019 11:58 am 
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Car Model: Saab 99 Turbo
Thanks chaps, I'll forward this to my local garage 8)

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PostPosted: Wed Aug 21, 2019 12:31 pm 
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Location: Longton
Peter, what % they are trying to get it under to pass? Assume you have checked they aren't applying the wrong regs?

Saab spec is lower than MOT requirement I think, as mentioned above 3% sounds ballpark correct, but for the MOT I understood it only needs to under 4.5% for 75-86 cars?

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PostPosted: Wed Aug 21, 2019 2:02 pm 
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Car Model: Saab 99 Turbo
Just looked that up and yes, you are correct. I'm assuming they know this at the garage... :shock:

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PostPosted: Wed Aug 21, 2019 6:39 pm 
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Joined: Fri Nov 17, 2017 7:21 pm
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Location: Aberdeenshire
Car Model: 1982 99GL
Pass mark is 4.5CO and 1200HC.

My first MOT with the 99 failed. Ask the garage if you can hook it up to the emissions tester yourself, this is what i did. Make sure it’s hot and rev it for a while to clear the system. Hook it up to the emissions tester and lean the mixture until it’s below the pass mark. The garage may be accommodating and do the emissions test straight away and carry on with the rest of the MOT.

After doing this at my first MOT it passed with 0.37CO and 47HC and has run very well ever since without changing the mixture.


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PostPosted: Wed Aug 21, 2019 7:16 pm 
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Probably just needs a tweek on the mixture, special tool required, goes in through the top with the dashpot plunger removed.
Might be worth checking the choke is shutting off properly


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PostPosted: Thu Aug 22, 2019 3:26 am 
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Location: East Fife.
Car Model: SAAB 96/MGB/Twingo/Niss Figaro
Peter
Not the same car, but my MOT tester has the same problem with my 1978 MGB.
He has to weaken the mixture down, to a point where the car will hardly run, to get it through. Fortunately he's an MG specialist, and knows the car very well, and is of course a classic friendly MOT tester.

I wouldn't stop doing the MOT test, after your car passes it's 40th birthday next year, just because it's not legally required any more. A false economy, that may come to bite you in the butt later.
You won't get your free VED/road tax till 1st of April 2021.

Andy


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PostPosted: Thu Aug 22, 2019 5:50 am 
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Location: REMAINING UNFAITHFUL TO FACTORY STANDARD SPECIFICATIONS SINCE 1988
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JUST AS AN ASIDES TO THIS 'STALE PETROL' I.E IF IT HAS BEEN SAT LONGER THAN 12 MONTHS CAN ALSO CAUSE THIS!

BIRDIE

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PostPosted: Thu Aug 22, 2019 9:00 pm 
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Car Model: Saab 99 Turbo
BIRDIEMANGO wrote:
JUST AS AN ASIDES TO THIS 'STALE PETROL' I.E IF IT HAS BEEN SAT LONGER THAN 12 MONTHS CAN ALSO CAUSE THIS!

BIRDIE


As always, very good point! The car has not run for a couple of years...

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PostPosted: Fri Aug 23, 2019 6:20 am 
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Joined: Thu May 05, 2011 4:39 pm
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Location: Auchindoun, Moray, North east Scotland
Car Model: Saab 99 T16 project
Peter, don't suppose they've reported troubles getting the bonnet open too?
Only mentioning this as my old white 99 had a lot of trouble one year, emissions very high and bonnet wouldn't open, guess which handle he thought opened the bonnet?

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PostPosted: Sat Aug 24, 2019 8:24 pm 
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:lol: :lol: :lol:

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PostPosted: Sat Aug 24, 2019 8:29 pm 
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Car Model: Saab 99 Turbo
99 Pete wrote:
Probably just needs a tweek on the mixture, special tool required, goes in through the top with the dashpot plunger removed.
Might be worth checking the choke is shutting off properly


A number of us have tried to do this (we have the special tool kit) but no luck, either the needle is buggered or it’s the jet it fits into. The car runs but it’s not happy...

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PostPosted: Sun Aug 25, 2019 9:34 am 
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Take the top off the carb and remove the piston Assy. Adjust the needle and check it is actually moving up and down. With the carb top off check the jet is approx 2mm below bridge in carb inlet. Sometimes they get punched down. Can't remember if that year used a choke modulating diaphragm but if this ruptures it can make mixture rich. Is it CO and HC too high or just one?


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