CWA

Been having troubles getting my car to pass MOT emissions.

Failed on CO (double the limits) and Lambda (a teeny bit over)

It's failed twice, the lamda improved second time as I fixed loads of blow holes in the exhaust. now lambda was only 0.006 over the limit. my main worry is the CO (still double).



I've just noticed that the exhaust manifold has a little gap between it and the block. I think it's leaking exhaust gases..
Would this trick Lambda sensor into thinking mixture was too lean (due to air entering system)..
And so make ECU richen the mixture
Hence causing higher CO levels?

Does this make sense? It's on a Polo as with my previous thread, have tried asking for advice on Club Polo but they are such scene queens I haven't got an answer lol

All help and advice muchos appreciated

Thanks, Chris

tabetha

If the blow is slight it won't double the CO, was the engine defo hot, ie fan had been on but gone off, a few degrees around the normal can make a big difference.
Any leak into the exhaust system is not going to help, in between every puff out there is a vacuum pulse drawing air in, lambda could be getting grumpy.
It may also just be the lambda, which my money would be on, have you means to check the switching speed, they tend to switch much slower when duff, and can give a decent gauge reading(voltage) but still be duff.
I assume the air filter is nice and clean/clear ?, mot place should have a good idea from full set of readouts.
If you need a new lambda, I can recommend ecolambda, pattern ones but do work, use these myself, around £25 work 100% perfect need to crimp some new ends on though, but are supplied.
tabetha

CWA

hi tabetha, thanks for the thoughts

i thought it may also be a lambda sensor aswell, so for the second time i put a different one in (was still second and so not sure if it actually worked still lol). im afraid i have no means of testing the switching speed, i only have a multimeter. i did however disconnect the sensor whilst the engine was running and it made no difference. does this mean that the sensor in is duff, and the engine is already running on the failsafe map (and so, really rich?) ?

As for the temperature, the test sheet said oil temp was 83 degs, not sure how hot everything else was though. the car had been standing around for ages though (2 months) without use, and only drove a mile down the road to the test centre. you think taking it for a spin and heating it up will actually help it pass? what about using redex aswell?

really unsure on this one lol so many possibilities! i hate emissions haha

cheers, chris

tabetha

Oil temp of 83C is not particularly not, oil temp is normally hotter than water temp, as it does cooling as well.
Yes defo take for a bloody good blast first, ace an excuse to speed, on a private road of course!!
tabetha