high emissions / error codes

[Adam32]

Despite putting some cleaner though the vehicle, my 2001 Saxo Furio has just failed the MOT on emissions for the Lambda reading on 2nd fast idle (reading 1.105). On the first fast idle test the CO was also high at 0.309 . The MOT tester suggested it could be a faulty Lambda sensor - what do people think?

One other thing to note is I sometimes get the engine management light come on the dash and the car seems to stutter badly. This is an intermittent problem as the last few weeks everything has been okay. When the problem occurred before I borrowed a neighbours computer and got the following two errors:

P0420 - Catalyst system efficiency below threshold bank 1
P0300 - Random / Multiple Cylinder Misfire detected

Do you think these problems are related to the emissions fail (although no lights were on the dash and the car was not stuttering during MOT test.)

Where should I go from here, do you think the problem is a faulty Lambda sensor? Where should I start? I have already replaced the spark plugs, fuel filter / air filter. Should I now replace the coil and the Lambda sensors? The less I can do the better as money is very tight.

[Shadowslayerzz]

Sounds like your cat is buffered mate, the reason why your having misfired is because when the 2nd lambda picks up higher co2 levels it tells the ecu to run a leaner mixture of fuel to combat it, I would say you're lambdas are fine as normally they will either give a reading or if faulty not give a reading at all, should probably change the manifold (which is where your cat is located as its a 01 reg) you can pick them up of eBay for pretty cheap and they're not hard to fit, there's guides on here of how to do it, just make sure you're changing it to a man I with a cat in it of another car and not a Dr-cat, the engine management light comes on as a result of the 2nd lambdas reading being too high.

[Chipwizards]

If you top lambda is tired and slow to respond it can cause the mixture swing to be excessive and going to extremes can cause a misfire.

You need to show us all the gas values for each test to make an accurate diagnosis. CO%, HC ppm, O2%, CO2% and Lambda.

Only knowing all the values can an accurate picture be seen, be that a lambda problem, a cat problem or a test procedure problem.

[smokeandpoke]

Just pay the man!