car failed on lambda 1.04 in nct advice needed

wsa30h

hi i have a peugeot 208 and it passed everything on the nct re test except the lambda which had a reading of 1.04 should be between 0.93 to 1.03. what are the most common causes and how do i fix it ?

Wanderer78

would fuel additive such as dipetane do much for this? id certainly try it before replacing sensor, lambda can in excess of 100 to replace....

Redex and a good hi revs gunning should clean it just enough to get through. Then a regular dose of redex every 6 months to keep the carbon down.

One of the main causes of carbon build up is inadequate oil changes. A routine of 6 month oil changes will slowly bring your emissions down. My old diesel van has zero smoke after 6 years of 6 month oil changes. Carbon build up causes various types of gas leak by which will all appear in the exhaust gases.

teediddlyeye

Fuel treatments are a waste of money for high lambda.

You've likely a pinhole leak in your exhaust.

Wanderer78

https://www.boards.ie/discussion/comment/120976119#Comment_120976119

would they knock it down into tolerance, just for test day, or just p1ssing against the wind?

teediddlyeye

https://www.boards.ie/discussion/comment/120976140#Comment_120976140

Wouldn't do anything.

A lambda reading over 1 simply means too much oxygen in the exhaust gases i.e running lean.

Almost always caused by a small leak after the lambda probe. If it was before the probe the ECU would see the excess oxygen and try compensate by dumping fuel. May have EML then as well.

Then the op would have a reading below 1. Most likely failing the other way.

User1998

You need to bring it to an exhaust specialist who can diagnose and test it properly.

I can recommend one in Dublin if your local

BrianD3

As said, the lambda of 1.04 with everything else passing means small hole in the exhaust. Run your hand along the length of the exhaust with the engine running (careful about the heat) and you may well feel a leak. If you put your hand over the end of it you may also hear it blowing further upstream. Smear exhaust putty wherever you think there is a leak and around joints etc. If the exhaust sounds different after you've done this, you may well have fix the leak (temporarily).

wsa30h

thanks guys am based in carlow i do think it could be an exhaust leak. may have hars words with the guy who serviced the car if that turns out to be the case.

teediddlyeye

https://www.boards.ie/discussion/comment/120977217#Comment_120977217

Do bring it to him to check alright. But bear in mind that it most likely wont be obvious at all, and he wouldn't have been under it with the engine running.

mk7r

https://www.boards.ie/discussion/comment/120977217#Comment_120977217

A service is a service (replacing serviceable parts like filters) its not an NCT checkup

section4

https://www.boards.ie/discussion/comment/120976220#Comment_120976220

Hi I failed nct on emmissions also, could you send me the details of this exhaust specialist please , he may be able to help

User1998

Auto Exhausts, Crumlin.

They have an emissions tester and fit catalytic converters etc.

wsa30h

try dipetane failed on emissions for co the first time but when i added dipetane i passed with flying colors for the emissions just have to fix the lambda.

Arthur Daley

I have seen this be a problem on VAG 1.2 litres. Eventually only solved by a rinse of dipetane and a bit of pot luck. Can depend on how it is tested it seems. Some will try with the high idle and some may not bother their Rolex.

It wasn't a pin head leak in the exhaust on inspection, or the lambda although that can't be ruled out initially.

wsa30h

got lambda changed passed on 1.03 on the dot in the failing limits section says not between 0.97 and 1.03 my lambda was 1.03.

blackbox

https://www.boards.ie/discussion/comment/121018314#Comment_121018314

not fixed then...

...If everything is working right it should be bang on 1.0 or certainly between 0.99 and 1.01.

wsa30h

the values for passing are between 0.97 and 1.03 not 0.99 and 1.01. its fixed but barely passed.