Did I get away with it last year somehow?

EoinHef

Had a very delayed NCT, due to covid backlog, toward the end of last year , 2012 Ford Fiesta 1.25l, and failed because the car was reading a high idle lambda of 1.07, the started limit on the NCT document is 1.03 so it failed.

The car has done 10k miles in 4 years so a friend told me to bring it on a long drive before the re-test.

I did this and the car passed, to my surprise it had tested at 1.07 again but now the NCT document said the limit was 1.09. Given it had passed the re-test I decided to just go with it. I have evidence of this in the form of the NCT reports.

So went for the NCT today, car tests 1.07 again and is failed. So my question is did I just get lucky with the person who passed it on the re-test last year? The car is 2012 and I can't find the limits based on year of manufacture online

Calahonda52

They are driving down the numbers to get older cars off the road

EoinHef

I still don't understand how the limit could be higher on the re-test though

hoodie6029

https://www.boards.ie/discussion/comment/121838526#Comment_121838526

What does the NCT manual say?

EoinHef

https://www.boards.ie/discussion/comment/121838630#Comment_121838630

"Lambda: In the case of vehicles first registered on or after 1 January 1994, the lambda value at either 2,500 rpm or at the

speed specified by the manufacturer is not 1+/- 0.03 or is not within the vehicle manufacturer’s recommendation"

Which to me means that the car should be reading between 0.97 and 1.03 which is the limit stated during my first test last year. Car tested @ 1.07 so it failed.

Yet the car passed the re-test with the same 1.07 reading. And the doc stated the upper limit was 1.09. So why would the limit be higher for a re-test?

EoinHef

Original test

Re-test

hoodie6029

They get that value from the manufacturer so it’s very strange that it changed from one year to the next.

Have you tried redex or dipetane in the tank for a week before the test? It could do enough to bring the value down to get you a pass.

Presume the car has been serviced recently enough?

EoinHef

That's in the same year, the re-test was 3 weeks after the initial test in 2023. I rooted out the 2022 NCT report and that says 1.03 as max limit, I reckon the re-test limit was a mistake and just worked in my favour that time!

Car was serviced middle of the summer 2023 which was about 3 months before the test.

I reckon ill just drop it into my local mechanic, know him well so won't be charged above and beyond and there must be something not quite right with it.

Failing that I'll try the additives, thanks for the advice folks 👍

teediddlyeye

A lambda reading over 1.00 simply means too much oxygen in exhaust gases.

9 times out of 10 its a small hole in the exhaust after the lambda probe.

Fuel treatment won't do sh1t.