Antipollution fault ?

[Agile]

My petrol 1974cc Peugeot 307cc 2004 year goes through long cycles of showing an antipollution fault.

Typically fault on for about seven weeks and then off for five weeks.

Can anyone suggest what might be causing the fault to be displayed and then to disappear?

There is no obvious change to the engine performance between either condition!

 

[Burnerman]

This often happens when the catalytic converter is getting unhappy......the fault clears after a good hot run but often comes back in time.
Make sure the lamp is off at MOT time!
John

 

[Agile]

The "off" condition occurred a few days before I needed to take it for an MOT.

So how to make my cat happy?

The off condition shows no obvious connection with long motorway journeys.

 

[Burnerman]

Keep the cat sweet by giving the car a good run as often as you can and it will look after itself.
John

 

[Avocet]

You really need to get a fault code reader plugged in and read the fault codes, so that you know which bit of the "anti pollution system" is being troublesome. Could be a lambda sensor too - or an airflow meter. There are various potions you can put in your fuel tank to clean cats, or various sprays to clean airflow meters (sometimes called "MAF"s). Maybe even try a few tankfuls of premium fuel that's supposed to "clean your engine"? When did it last have a set of plugs?