Toyota RAV4 failed MoT on Emissions

[Sakhmat]

Just MoT'd my 1997 RAV4, with 113K miles on it.

Failed on emissions.

Two idle tests:
CO limit is <=0.300%, actual value 6.795%, 6.949%.
lambda limit is 0.970-1.030, actual value 0.795, 0.785.
HC ok.
No engine warning lights on dashboard.

From the above figures is it possible to home in on what needs replacing? Cat? Sensors? Other? Could it be a result of over-warm engine (I think engine runs warm because the electric fan runs a lot)?

Cheers, Bill

Edited by Sakhmat on Thursday 27th August 02:06

[banzai_dan]

Sakhmat said:

Just MoT'd my 1997 RAV4, with 113K miles on it.

Failed on emissions.

Two idle tests:
CO limit is <=0.300%, actual value 6.795%, 6.949%.
lambda limit is 0.970-1.030, actual value 0.795, 0.785.
HC ok.
No engine warning lights on dashboard.

From the above figures is it possible to home in on what needs replacing? Cat? Sensors? Other? Could it be a result of over-warm engine (I think engine runs warm because the electric fan runs a lot)?

Cheers, Bill

Edited by Sakhmat on Thursday 27th August 02:06

Your air/fuel mixture is too rich. I.e. the engine is injecting too much fuel. The most common cause of this is a faulty lamba sensor.
That's all the help i can give you i'm afraid.

[Pumaracing]

Struth that's running rich. Most likely the lambda sensor has failed and is only outputting a very low voltage making the ecu think the engine is running lean and hence it keeps injecting more fuel in. Easily checked with a voltmeter. If it's working ok the voltage should rapidly fluctuate up and down around a mean of 0.5v. If yours is only putting out much less than 0.5v you have your answer.

[Sakhmat]

Hi, thanks for your replies.

It turned out to be the oxygen sensor. When replaced, the emissions figures were immediately perfect.

Sincere thanks to A.W.Autotech, Aberdeen. They did a superb job to fix the problem - I recommend them wholeheartedly. Wonderful people.