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[downsmen]

Hi
Took my car to MOT failed on emissions on CO levels
Fast Idle 0.728
Second Fast Idle 0.804
Natural Idle 0.284

It Passed on everything else
There is No error codes being displayed
I have Changed Plugs and oil

I welcome anyones help in letting me know what could be wrong.

[Black cxd v6]

Had a Metro that failed on emisions. Passed after a 300 mile trip on the A1

[Kevin Wood]

Does the emissions test report contain a Lambda value? Can you post the rest of the information on the report?

Does the car warm up quickly after a cold start and does it run at the correct temperature (roughly middle of the gauge)?

Any other starting / running issues? Any trouble codes in the ECU? (might be worth paperclipping it or using a code reader just in case).

Oh, and welcome to the forum.  

Kevin

[Martin_1962]

Take it for a fast drive including a lot of full throttle full RPM.

[downsmen]

Hi Kevin

here is the full report

Fast idle

CO           0.728
HC           161
Lambda    1.022

2nd Fast Idle

CO           0.804
HC           164
Lambda    1.017

It Warms up okay usually just under Half in the gauge
It stalled a few times ( Automatic) on the way home from the mot but that is really the first time its done that.
Occasionaly the revs drop when pulling up to a junction and trys to stop.

The Garage pluged there reader in whilst at the mot and said there was no error codes

Thanks for you help

Paul

[Kevin Wood]

It's running a little lean looking at the Lambda value but it's not that far out.  :-/

I would try the following:

Give the breathers, throttle body and idle air valve a good clean out and check for air leaks in the induction system

Run some injector cleaner through the fuel system.

Check for any leaks in the exhaust system.

If that doesn't clear it I'd get it on a code reader that can view live data and check that the ECU is seeing correct readings from the temperature sensors, that the Lambda sensor appears to be operating correctly ahnd that nothing else is suspicious.

.. and a good blast up the motorway before the re-test is never a bad thing, especially if the car does mainly short trips.

kevin

[downsmen]

Cheers Kev i'll try that

Thanks for your help i'll let you know what happens

Thanks again

Paul

[magnul]

The lambda value says lean, whereas the CO means exess fuel, i.e. rich. I'd say a vacuum leak is playing up the lambda signal. If you have a decent voltmeter you can easily check what kind of signal you get from the lambda.
E85 is brilliant for bringing down CO levels, but AFAIK it's hard to find in UK.

[Kevin Wood]

The lambda value says lean, whereas the CO means exess fuel, i.e. rich. I'd say a vacuum leak is playing up the lambda signal. If you have a decent voltmeter you can easily check what kind of signal you get from the lambda.
E85 is brilliant for bringing down CO levels, but AFAIK it's hard to find in UK.

It could be that the cat isn't working effectively due to the lean mixture. You'd get some CO then, even if it was lean. However, I agree that a leak, in the induction, or more likely exhaust system is a possibility.

I would expect the ECU to raise a fault if the Lambda sensor has failed, but it could of course just be on its' way out and not totally failed.

Kevin

[tmx]

or take it to another garage that doesnt poses an emissions machine!

[magnul]

It could be that the cat isn't working effectively due to the lean mixture. You'd get some CO then, even if it was lean. However, I agree that a leak, in the induction, or more likely exhaust system is a possibility.

I would expect the ECU to raise a fault if the Lambda sensor has failed, but it could of course just be on its' way out and not totally failed.

Kevin

The get-rid-of-COandHC-part of the cat should work just fine under lean (oxidising) conditions. The lambda can decay for quite a while before a fault code pops up. Mine was half dead for at least 2000km before the ECU understood it.

[Albert1]

Try Cataclean, although it may take a while (several days) to finish pushing the crap out the tailpipe, before emissions improve.

[toller]

Mine failed on a high CO reading a couple of years ago.  In the end I discovered it was because one of the cats was on it's way out.

However before I took it for a retest I gave everything mentioned above a quick onceover, put some optimax in and took it for a blast up the motorway, never shifting above 3rd gear so the cats were really hot.

It passed (only just she informed me).

Ended up replacing the drivers side cat about 3 months later whn it started to rattle.

[magnul]

Try Cataclean, although it may take a while (several days) to finish pushing the crap out the tailpipe, before emissions improve.

Well, all the cataclean in the world won't help if the engine is overfueling. I''d start with a check of the lambda sensor and take it from there. Still, I agree that running the car like you stole it is a good idea prior to MOT.

[Lazydocker]

I always try to give my cars a good hard drive on the way to the MOT station TBH... I'd say it's probably a leaky exhaust too