Emissions on the edge.

[THORNOGSON]

Took the 97 Chimaera with 25,ooo miles on the clock for its MOT today, and it struggled with the emmission test. The lambda value on the fast idle test was just over 1.03. After about 30 mins and several attempts the value fell to 1.03 so just scraped thro'.
Anyone any ideas where to start to diagnose what is wrong.
Graham.

[spend]

Graham, it is possibly just that the pre-cats have been removed - these assist when cold. With most cars its better to give them a good thrashing to warm the cats up immediately prior to the emissions test. Old ones seem to work OK but take a lot longer to become fully operational ( which I believe is part of the manufucturers approvals, but not the MOT test).

Dave

[harrow_chim]

Um - possibly a faulty/dying lambda sensor. A TVR dealer/specialist would be a good place to go for a diagnosis.
Nick

[greg_D]

My pug 306 dog transporter struggled with the emissions at it's last MOT, it turned out to be a small leak from the front section of the exhaust , not a blow as such but enough to muck up the emissions

HTH

Greg

[Mr Jenks]

What were the other readings? CO CO2 and HC? May be able to tell a bit more with those as well.

[thornogson]

fast idle
2500 to 3000rpm 2840rpm
co 0.2% 0.00%
hc 200ppm vol 2ppm vol
lambda 0.970 - 1.03 1.03

natural idle test
engine speed 450 - 1500rpm 923rpm
co 0.3% vol 0.00% vol

[Will Perry]

Hiya mate.... Check out number 5 on the following page....

www.bobmckay.co.uk/p_emissions.html

Regards, Will...

[Mr Jenks]

Sounds as if it may well have a small leak in the exhaust. It does not have to sound like its blowing but it can draw in air. The O2 reading will normally be high if that is the case.
Dave

[chimtvr]

probably an exhaust leak try putting the probe up the other pipe a reading above 1 indicates a lean mixture (or exhaust leak) below 1 rich mixture the cats will not affect this reading they only affect co and c02

[thornogson]

Thanks guys, the probe was tried up both pipes with the same result. I will check for a exhaust leak first, then a weak mixture. Is it possible to do this yourself, "bible" seems to say take it to a tuner.