CO emissions too high

[NikPegg]

Failed controle technique (French MOT) due to high CO levels.
1998 1.4l petrol Partner. 237 500 km

Hello! My Peugeot Partner has just failed its CT for high CO levels (amongst other minor details!) I've added a fuel injector additive to the petrol; added an engine "repair" additive to the oil and no difference. My local garage (non peugeot) has done a quick diagnostic which says the lambda sensors are OK, but I read somewhere that they should be changed between 80 000 and 160 000 km. Mine have Never been changed :S No difference to the CO levels after the additives. Any ideas on sensors or is the engine just too old? Its had the head gasket changed twice, and the distribution belt changed twice as well. The catalytic converter was changed a year ago. Any suggestions would be very welcome.

[homeruk]

Have you done an air filter change , oil and filter change recently?

Do run your engine hard before the test? (This can help)

[Gadgetman]

Does the engine run hot or is the temperature normal?

Any sign of oil in the coolant?

Have you checked the compression?

Lambda sensorS? As in more than one?
(One before and one after the catalytic converter)
Didn't think a 1998 had two, just the one before the converter.

There's been no warning lights on the dash?

[NikPegg]

Have you done an air filter change , oil and filter change recently?

Do run your engine hard before the test? (This can help)

The oil & filter were changed fairly recently before the MOT, but I'm not sure about the air filter (i've been trying to get hold of a Haynes manual, cos the french equivalent is worse than useless!!) Now that i've got one, I'll have a bit more confidence to do things As I mainly do short runs, I'll give it a good run before next checking. Thanks

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Does the engine run hot or is the temperature normal?

Any sign of oil in the coolant?

Have you checked the compression?

Lambda sensorS? As in more than one?
(One before and one after the catalytic converter)
Didn't think a 1998 had two, just the one before the converter.

There's been no warning lights on the dash?

Engine temp is normal.
No sign of oil in the coolant.
You're right about the lambda SENSOR; its my MK2 (bought out of necessity to replace MK1) which has 2.
No warning lights on the dash, either.

How does one check the compression?cratch: Thanks for your suggestions.

[Gadgetman]

Generally, the way to check compression is to pull the spark plugs, then fit a compression gauge in the plughole of one cylinder, crank the engine a couple rounds, read off the gauge, move it to another cylinder, repeat...

The pressure should be around 10Bar somewhere, and max .5Bar difference between the cylinders.

[ron]

As per Gadgetman but if pressures are low,repeat(on a warm engine) after squirting some oil into the cyls.If the pressures increase significantly,it's ring/bore wear.alut: