MOT failed on emissions

My Peugeot 306 Meridian just failed its MOT based on its high emissions despite having a new catalytic converter and lambda sensor. Any ideas what it could be? I really dont want to pay even more money to someone that clearly doesnt have a clue.

Asked on 6 May 2011 by gilky

Answered by Alan Ross
Well firstly would suggest that you check your air filter to se if it is clogged up at all. It would appear that your air /petrol mixture is not correct. If the air filter is ok, then I would suggest that you check all your air pipes after the MAF (mass air flow sensor) to make sure that they are not spilt /disconnected as this again will effect the balance.
If no splits etc, the you should check the MAF itself, try cleaning it if it is dirty etc. It maybe that you have to renew it, although a good mechanic should be able to diagnose this.
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