996 3.4 failed MOT Emissions test, help needed please.

[t955daytona]

Hi all,
My 996 has just failed the emissions test during the MOT. The CO and Hydrocarbons (hcc) are fine but the lambda reading is out of spec 1.045 instead of less than 1.03. The car had had a good run and was hot, both the lambda sensors are performing correctly( one is new) and the readings are almost identical out of both exhausts. The car has just had a service and has had plugs and coil packs in the last 2k miles. The exhaust is not leaking. Myself and my mechanic are scratching our heads as to what it could be. My next move will be to change the cats although I would of thought that if they were shot the co/hcc would be out. Any ideas gratefully received.

As an aside, has anyone used these http://www.ebay.co.uk/itm/Top-Gear-Tuning-Porsche-...

As they seem to be well built and cheaper than OE cats.

Regards Craig

 

[eca02apc]

Hmmm, got me on that one! But with regard to the cats, Top Gear are the sister company to Kline; and a few people on here have got Kline exhausts.

 

[t955daytona]

Thanks for that, if I'm going to try new cats I will try those.

 

[t955daytona]

Has nobody got any ideas, it had a new MAF 6k miles ago and 1 new lambda last year, my understanding of the reading is that it is running a little lean so I am not sure wether new cats would fix it. Could it also be a slightly split air/oil separator?

 

[quattrosteph]

Get it checked properly by a Porsche specialist before replacing parts ....

 

[t955daytona]

Get it checked properly by a Porsche specialist before replacing parts ....

Its at one now but they are scratching their heads also!

 

[SimonW]

Perhaps try another MOT station. Could be their end ? A another £55 test fee might be cheaper than trying/buying new parts, even if just to reconfirm before you started spending more ?

 

[quattrosteph]

Make sure you have good petrol in the tank. Tesco99 or Vpower are the best. I have a friend who had some problems with his new car after putting some Sainsbury's petrol.....Car wasn't running right......Burn all the petrol you have and put some good one and go somewhere else for the MOT .

 

[t955daytona]

I have tried all that. 3 different test stations! I always use Vpower etc and even tried a cat cleaner and gave it a proper spanking to get it warm. I am slowly running out of ideas!

 

[quattrosteph]

May be your cats are shot. Time for a sport exhaust then. Prestige Salvage do sale second hand parts too.

 

[quattrosteph]

Take the cats off and inspect them.

 

[quattrosteph]

Take the cats off and inspect them.