Emissions

[NickFr]

Right assuming that you have a Reno Cat and new Lamda sensor fitted to a Williams, could it still fail the emssion test?

If so could it being chipped and remapped make a difference?....what else would cause it to fail?, induction kit etc.....

Ta

[TriO`]

blowing exhaust can...


mine failed when it had a hole in the exhaust

[Anders]

The lamba is basically just a glorified oxygen sensor. It basically creates its own voltage based on the unburnt oxygen content in your exhaust gas. Feeding this back into you ECU to either richen up your air/fuel mix or lean it out, basically trying all the time to keep a balanced ratio of 14.7:1 (stoichiometric mix).

Can you get hold of the readings? Was it a fail on idle, or fast idle? A good way to tell where the cause is, is by attaching a voltmeter and seeing what the reading is...average is around 0.4-0.5V.

High voltage output (rich) from sensor will cause ECU to lean out the mix, resulting in high hydrocarbon emissions. Possibly due to bad MAP or airflow sensor.

Low voltage (lean) from sensor will tell ECU to pump more fuel in, which will give you more carbon dioxide emissions. This is normally because the sensor is knackerd (which you have replaced) or you have a vacuum leak somewhere.

The sensor is on a closed loop circuit (when up to temp) so doesn't know anything other than oxygen content. Somewhere you are getting a leak, or even as the sensor is grounded by attaching to manifold, check the voltage drop across sensor body and engine block. Could be a bad earth, if no leaks are found.

[NickFr]

Cheers Anders, in fact I have not changed the Lamda yet, I had the Cat fitted and it still failed!...I am going to have the Lamda fitted tomorrow, many thanks for your advice.

Trio, there is also a very small hole in the exhaust...Ta for the tip

[peteskye]

Different car, but same thing.

My other halfs Mk3 gti failed on emmisions, so a new i fitted a new cat and lambda sensor - thought that would be it... no... took it back in on monday and the emmisions were worse than ever the co2 level is supposed to be 0.3 max, and it was reading 12. something, and the lambda was well over as well -- in fact failed on all co2 limits, so took it for a thrash and straight back in, was a bit better, but still failed.
Only cos the guys in the garage were really good, did it pass - we took off the air filter, and there was an air inlet flap that was stuck, so freed that off and was allot better, but still failed, in fact the only way we got it through was to put a clamp on the idle air inlet hose, and so less air went in, and it scraped through.
They reckoned it was one or 2 of the injectors taking in air and needed a look at? could be that wi yours? or sneak a clamp on the air in?

easier wi my knacked old isuzu a couple of years back -- just ran it on parrafin for 15 mins -- flew through..

Pete