Do I need a standard back exhaust box to make lambda work?

prelerepairman · Post by **prelerepairman** » Sat Dec 12, 2015 12:39 pm

My 2.2vtec 5th gen is failing CO at .68%vol and Lambda is 0.003 over ( reads 1.033 when needs to be 1.030 )
My mot guy says the computer thinks the exhaust has a leak and is continually retuning fuel flow?? He suggests it needs a normal back box to give back pressure to stabilise the system - I've an old stainless steel system with fat back box with removable baffle-. Do any of you pass mot with your fat back box fitted?
Anyone familiar with this problem?...any ideas? Anyone in Central Scotland got an old back box so's I can see if one'll fit onto my system . No one stocks new ones up here for me to measure. Thanks guys.
Car is H22A8

chrismc · Post by **chrismc** » Sat Dec 12, 2015 12:47 pm

I think he's talking rubbish.

1. Give the car a proper caining immediately before the test to get the Cat super hot. Should pass then

2. If not then you are looking at a Lambda IMO

If the exhaust rear of the cat is in good condition then it really shouldn't mess up the Lambda readings. Ignore the back pressure guff

prelerepairman · Post by **prelerepairman** » Sat Dec 12, 2015 1:10 pm

Thanks Chris. I gave car (H22A8) very hot run for both mot tests...no diff!
Is Lambda a screw in fitting or a section of pipe?
My previous Preludes (2.0l) had a plug at manifold/heatshield but this car seems to only have a plug/wire just before the flexi joint before cat. and no wiring after the cat. Is this correct?
Thanks again.

Post by **Vtecmec** » Sat Dec 12, 2015 1:15 pm

'Yes, the o2 is just before the flexi.

prelerepairman · Post by **prelerepairman** » Sat Dec 12, 2015 1:29 pm

I see it screws in!
O2 means Lambda sensor!

Post by **vanzep** » Sat Dec 12, 2015 2:23 pm

O2 sensor screws into downpipe if thats what you mean

prelerepairman · Post by **prelerepairman** » Sat Dec 12, 2015 3:23 pm

Cheers, I see now. Thank you.

Post by **vanzep** » Sat Dec 12, 2015 10:05 pm

just buy the whole exhaust system i have up for sale and the cat and downpipe and be done with it

YouTube · Post by **Sailor** » Sat Dec 12, 2015 10:20 pm

vanzep wrote:just buy the whole exhaust system i have up for sale and the cat and downpipe and be done with it

Doesn't fit a 5th Gen, though ...

... or does it?

Post by **vanzep** » Sat Dec 12, 2015 10:32 pm

Just needs one hanger on the backbox relocated

i know you have to also look at cat size and downpipe size depending on if it is A5 or A8 engine.