MOT emissions fail guide / database

[Dox 23]

I've just had my VR6 fail on emissions and was offered this advice by an online friend - it maybe of use to others?

 

Does it need a cat test

 

 

 

EMISSIONS HELP

 

CO high, co2 low hc high, o2 high - rich mixture with ignition misfire

 

CO high, co2 low hc high, o2 low -faulty thermostat or coolant sensor

 

CO low, co2 low hc low, o2 high - exhaust leak after cat

 

CO low, co2 high, hc low, o2 high - injector misfire, cat ok

 

CO high, co2 low, hc medium to low, o2 high - rich mixture

 

CO high, co2 high, hc high, o2 high - injector misfire, cat not working, combination of rich mixture and vacuum leak

 

CO low, co2 high, hc low, 02 low, good afr and cat operation- system normal .

 

 

lambda typical range 0.97 to 1.03 [ ideal lambda 1 ]

The emissions limits to be met are specified for both the fast and normal idle tests. At fast idle, CO must be at or less than 0.2%, HC at or less than 200 parts per million (ppm), and the lambda value(1) must be between 0.97 and 1.03. At normal idle, CO must be at or less than 0.3%.

Edited April 7, 2016 by Dox

[swiftkid 1]

There is a loophole for those with engine conversions struggling with emissions, if your car is aged between 92 and 95 and your car is not listed on the analyser database (as specified on page 9 above) then you get 3.5% rule. But here's the twist, a corrado vr6 or corrado 1.8 will be on the database but a corrado r32 or 1.8t will not!

 

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