996 C2 MOT emissions fail :(

Hi all Took my 98 C2 for MOT today (month early ). Passed on everything but emissions. Standard exhaust and no other mods. Car has not been used that much recently - I bought it a couple of months back and it had been stood and only done 3 or 4 thousand miles a year over last few years and ive only really used it locally bar the odd 70 mile srun, since ive been fettling the car. Also it was previously running too cool, I had a new thermostat fitted to rectify (there was none in when i got the car) so there could hve been some over fuelling etc. Natural idle test - pass Fast idle test fail CO 0.47 % HC 27ppm 1.044 Second fast idle test CO .40 HC 10ppm 1.090 Not far out but still failed ! Tried taking the car for a half hour run and that improved things slightly. There are no warning lights on the dash and the car runs fine. Fresh oil / filter and new air cleaner. Have been advised to run some fuel system cleaner over the next week or so and give it another try (they will test it free). So my questions are a) has anyone else had this issue and managed to sort it and b) is ther a recommended fuel system cleaner (ive put some unipart in the tank for now). My intention is to run a couple of fuel cleaners and give the car some runs over next week or so before re presenting it for emissions test - if it still fails it will be plan b and booked into local Indy !! Regards Dave

Mine recently almost failed the mot, the guy said one of my cats maybe needs replacing but not yet. He did mention tho that the emissions test doesnt like cars with 2 separate exhausts. The new mot sheet you get is a bit weird tho.

I would get a local indy to run a diagnostic check on it as it could be the lambda sensors or airmass meter that is failing. It wouldn't do your cats any good if they are. If you know someone with a PST2/PIWIS or Durametric they can hook it up to see if any faults are logged and have look at the live values.

go for a run in second and third and get the revs up , the cat will get red hot and clear, do this a few times and do it just before mot.

I agree with Barry,thrash it mercilessly and if it fails again,well,at least you've had a good time 'fixing it'

Where I live they refer to this as a Chinese tune up!

Thanks for the suggestions guys ! Beauty is I have just under 4 weeks til the mot expires and 2 weeks for the free re test. Been doing some reserach and came up with a few products that may help, or may, in fact do nothing at all !! Below is a product purported to be just what im looking for : http://www.cataclean.com/index.html This is the really cheesy sales pitch / information film on youtube: http://www.youtube.com/watch?v=DrkYw0Ks2-Q Very dubious as to whether this is going to do anything ! Also a "pre mot" clean burn emissions reducer from Wynns thats on the market : http://www.halfords.com/webapp/wcs/stores/servlet/product_storeId_10001_catalogId_10151_productId_274571_langId_-1_categoryId_255221 Probably worth trying one or both of these then doing an "Italian Tune Up" prior to re testing emissions. If no joy with that then a hook up at local indy to see if theres anything else amiss should do the trick ! Cheers Dave

Italian tune up with Shell's finest!!

Get some of the Forte fuel treatment for petrol engines. Put it in a 1/4 tank of Super Unleaded and go for a 30 mile blast. The Forte stuff is very good and I use it in all my cars. Makes a noticeable difference after treatment in just about every vehicle, even in my T4 van! Alasdair

as per advice above go take the car for a really long run and get the cats hot, use the car a bit more often porsches( like any car ) need to be used cats only start working properly once hot if they are used for lots of short runs they get choked for want of a better word and stop working efficently I would avoid fuel additives beyond petrol, cats can fail but I would definately try the above first,good excuse to go on a hoon to Scotland [ ]

Fiend a "friendly" indie to get through the test, then replace your cats when you can.

Off to Euro Car Parts or GSF this week for some "Cataclean" - they both stock it - will try it and report back on comparison on the emissions test !! Fingers crossed !!

I would do what Min suggested and get the fault codes read by someone with a Porsche tester, not a generic test tool. If the MAF or a lambda sensor is playing up, all the fuel treatments and Italian tune-ups in the world aren't going to do any good. If the DME is over-fuelling due to a faulty sensor it could explain the problem. And no, you would not get an engine check light if there was a faulty sensor on a UK car. Just ny 2p's worth.

Thanks all for the advice, will update in due course. I think over fuelling has certainly been taking place when there was no thermostat in the car and she was running too cool until I had it checked out and a stat fitted. Regards. Dave