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Hi All

Am after some advice. My 3.2 Carrera has just failed it’s MOT on emissions. Car has been in storage for the last 12 months or so. Has never failed on emissions before. 
 

Has anyone else had experience of this? Any advice on the way forward very gratefully received. Many thanks. 
 

Sam

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What was the result?

A really good blast getting it good and hot can often sort things out, especially if it had not run long/hard enough to get rid of all the oil that is bound to have accumulated in the cylinders and exhaust after a long period standing.

Mark

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Does the 3.2 have a decel valve? If so pop the top pipe off before you go in.

But as Mark says, never take your car in cold.

Also, your MOT man can bypass the emissions test altogether if they want to. Might be worth finding a more amenable garage. What year is yours?

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1 hour ago, Planty said:

Hi All

Am after some advice. My 3.2 Carrera has just failed it’s MOT on emissions. Car has been in storage for the last 12 months or so. Has never failed on emissions before. 
 

Has anyone else had experience of this? Any advice on the way forward very gratefully received. Many thanks. 
 

Sam

Same thing happened to me last year. The Porsche specialist with whom it was entrusted told the MOT tester to stop being so stupid...

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They run proper rich if anywhere near cold.  As suggested give it a good spanking and then take it back.

My MOT tester will tweak the result if it's not far off a pass.  Apparently it all depends how far the probe is stuffed up it's chuff.

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Yup, really good blast "on your way" to the tester will help. Or as Phill says, a friendlier garage. Boys up by me are rally guys so they usually tweak the results by revving up etc if needed. 

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13 minutes ago, Nige said:

  Apparently it all depends how far the probe is stuffed up it's chuff.

Said the Doctor to the ...................................................................

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Took my wifes Boxster for an MOT and ending up popping the probe up a Vauxhall Corsa in the next bay, passed easy.......:P

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Thanks all. The tester took it for a blast after initial failure, but still failed. It’s a late ‘83 3.2. 
 

my exhaust system Is knackered (but just ok to pass the MOT). Could this contribute to the problem? 

And can anyone provide a picture of a decel valve? Not sure if I have one. Apollo goes for being useless!!!

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What parameter did it fail on?

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Has it been serviced recently Sam? Maybe just running a little rich? 

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Mmm.... I don't think a 3.2 has a decel valve.

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What year/month is your 3.2?  What did it fail on CO or HCs?

The limits change on CO% from 4.5% to 3.5% from August 86.  (HC remains at 1200 ppm).

A car running very slightly rich may be close to the 3.5% limit but should be well clear of 4.5%.  Shouldn't be any problem being way lower than the 1200ppm on HCs unless imperfect ignition or more serious general engine health issue?

On a warm engine after a good blast I'd certainly expect to be within these limits

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Take it to my man, at a recent MOT he looked around the car and he printed the certificate. Only afterwards did he ask if I wanted it put on the ramp and tested..... No names, no address for obvious reasons.

Find a more sympathetic MOT man.

Chris.

 

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+1 on finding a more amenable garage. My garage don’t bother with the emissions when I’m having mine done. If you’re in Kent or willing to travel PM me for details.

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you guys.. you are really running your 911 at this CO level--it is kinda insane??.the max if ever without the cat should be 1,5-2%......

The limits change on CO% from 4.5% to 3.5% from August 86

 

Ivan

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1 hour ago, proporsche said:

The limits change on CO% from 4.5% to 3.5% from August 86

 

Ivan, that is the UK emission testing limits, not we are running our cars to

Edited by SilverWT

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What ARE we running our cars to?

Mine is a micro-smidge under 3% and is consistent at each MOT test.  I even use the known stability of my 3.2s CO% level as a means of roughly calibrating a cheapo CO meter that I use to set my Lancia.

Haven't adjusted my car in any way since last Wayne Schofield RR Map.   3% is still perfectly safe IMHO and certainly not crazy rich.  AFR of 13 rather than theoretical perfect of 14.7 is good compromise to ensure optimum power and smoothness without risk of issues by going too rich.

 airfuel.jpg.f64e431956dcfb48c726a6f68dfae6be.jpg

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28 minutes ago, SilverWT said:

 

Ivan, that is the UK emission testing limits, not we are running our cars to

I C....but still limits like this for 911 who set it up???The car cannot run on 3,5-4% CO..;-)))))))))))0

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What should it run at Ivan? 

And what about '80 SC's? 

Not hijacking your thread Sam, just thought I'd ask about earlier CIS cars while it's being discussed 🤔

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1 hour ago, proporsche said:

I C....but still limits like this for 911 who set it up???

It's not 911 specific, all petrol vehicles of that age.

Mark

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My last MOT emission results:

 

1984 3.2 - CO = 0.76%, HC = 46ppm

1983 SC - CO = 1.82%, HC = 52ppm 

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36 minutes ago, SilverWT said:

My last MOT emission results:

 

1984 3.2 - CO = 0.76%, HC = 46ppm

1983 SC - CO = 1.82%, HC = 52ppm 

perfecto;-)

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54 minutes ago, SilverWT said:

My last MOT emission results:

 

1984 3.2 - CO = 0.76%, HC = 46ppm

1983 SC - CO = 1.82%, HC = 52ppm 

My 89 3.2 - CO = 1.7%, HC = 70 ppm

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2 hours ago, proporsche said:

I C....but still limits like this for 911 who set it up???The car cannot run on 3,5-4% CO..;-)))))))))))0

On what basis do you make this claim?

3.5 / 4 % broadly speaking is only just under an AFR of 13 which is far from excessively rich and still below levels equating to theoretical optimum power.  My car has run at 3% for years and I couldn't see another 0.5% increase making any significant difference.

Conversely I would be far more concerned if my CO% was much below say 0.75%, i.e. AFR > 14 

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