Mot Emissions Failure

[gazbrown]

Hi guys and girls, my 99 celica vvti 140 failed its MOT today on emmisions, specifically fast idle CO levels. On the first run it was 0.68 % and the second it was 0.77 %. The level as i'm sure you know is supposed to be less than 0.30 %. On the natural idel test read 0.50% which is bang on the limit. It passed the rest of the emisssion tests with ease.

The guy in the garage said it could be the lambda sensor is dirty and to give it a clean with WD40. Does this sound right ?? I don't know much about emissions but there is a lambda reading on the test which is within limits so if the sensor is not working correctly should it not effect this reading ??

If it is the sensor where does it live ??

In addition my car is burning alot of oil, is this related ? Can't see any leaks or blue smoke

Thanks in advance

[Paulo_J]

A high CO level means you have incomplete combustion. As modern engines are computer controlled, the sensors are the most logical place to start; if it was a physical problem with the engine itself or a sensor was completely dead, you wouldn't have passed the hydrocarbons test (and you'd probably notice it wasn't running properly). Giving the lambda sensor a clean seems like an easy and cheap thing to try first.

I'm not familiar with your particular car, but the lambda sensor measures oxygen levels in the exhaust gases so is most likely in the exhaust somewhere close to the outlet manifold - you should be able to spot something plugged into the exhaust pipe.

It's probably worth changing the air filter too if you haven't done it recently, as this can restrict the air intake if it's clogged.

[gazbrown]

A high CO level means you have incomplete combustion. As modern engines are computer controlled, the sensors are the most logical place to start; if it was a physical problem with the engine itself or a sensor was completely dead, you wouldn't have passed the hydrocarbons test (and you'd probably notice it wasn't running properly). Giving the lambda sensor a clean seems like an easy and cheap thing to try first.

I'm not familiar with your particular car, but the lambda sensor measures oxygen levels in the exhaust gases so is most likely in the exhaust somewhere close to the outlet manifold - you should be able to spot something plugged into the exhaust pipe.

It's probably worth changing the air filter too if you haven't done it recently, as this can restrict the air intake if it's clogged.

cheers i'll give it a shot. found a link for the manual so at least i know where they are located