MOT Failure: Emissions - possible causes?

[James28]

My car failed on Emissions.
-Exhaust emissions carbon monoxide content after 2nd fast idle excessive
-Exhaust emissions lambda reading after 2nd fast idle outside specified limits

It failed on CO Level on first test, and CO Level and Lambda reading on second.

Fast Idle test:
CO Level: 1.03% (Limit <0.20)
Lamda: 0.98 (Limit 0.97 - 1.03)

Second Fast Idle Test:
CO Level: 1.40%
Lamda 0.96

I have a Yozza exhaust, and normally run it with a decat, but swapped the cat back exactly a week ago purposely for the MOT.
What could be the possible solutions?
-Replace the pre-cat Lambda sensor? I know the post cat sensor is fucked but that wouldn't cause it to fail?
-Could it be an issue with the cat being sitting around in my garage all year, or only recently going back on? (Before the test I went for a 'spirited' drive as recommended)

I turn my emissions light off when it comes on with my RS Tuner, because of the decat.

Any help would be appreciated!

 

[sinnie92]

Did they block off one tailpipe to test?

IIRC a specialist on here mentioned it can give false readings if they don't

 

[James28]

I don't know. doubt it. Can anyone confirm if this is the case?

I don't want to pay for a new lambda if its not actually that and just an error of reading, or to do with only recently swapping back to the cat.

 

[Neal 182]

High lambda reading will most likely be down to the exhaust blocking the one pipe off should help/sort that. I'd be booking a retest and getting it very hot before taking it back

 

[sinnie92]

There needs to be a 'pre mot checks and what to tell the technician before hand' sticky

 

[James28]

Would that affect CO readings though?

 

[scaryopa]

Few weeks ago i had mine fail on exactally the same, i put some Forte Cleaner through it and ran it as normal for a week then took it out for a damn good thrashing befor the retest and it passed with flying colours. Btw my Lambada was playing up for months intermittently messing around and it passed with that. Since been replaced. Also It hasnt has a set of plugs since 2010!

 

[sinnie92]

Few weeks ago i had mine fail on exactally the same, i put some Forte Cleaner through it and ran it as normal for a week then took it out for a damn good thrashing befor the retest and it passed with flying colours. Btw my Lambada was playing up for months intermittently messing around and it passed with that. Since been replaced. Also It hasnt has a set of plugs since 2010!

You slack b*****d

 

[scaryopa]

You slack b*****d

Sorry to hijack

Saw a recipt for plugs when i got the car few months ago and thought it was from the last service, checked yesterday and saw it was 2010! Bit shocked... so plugs are in the post on the way Just another thing to add to the list that hadnt been sorted or mantained properly.
She looked a good buy when i went to view her, would appear looks are misleading, spend Alot on just TLC to get her right, but worth it imo.

 

[James28]

I've ordered a new Lambda from ECP for £53 anyway.
Hopefully that'll sort it. And the fact I'll have been driving an extra week with the cat.

 

[KFRRS94]

If your pre-cat sensor is fooked, then it could be over fueling. Which will put a lot of s**t in your pipes.

I had to replace my cat & pre-cat sensor to pass my MOT 2 weeks ago.

 

[ben lee]

no need to block the exhaust to pass.

looks like a faulty lambda sensor,coolant sensor,engine not up to temp or a poor re-map.

can you use the RStuner to see the lambda and coolant sensor values?

 

[MG cup]

Is the air filter clean?

 

[ben lee]

Is the air filter clean?

wont effect emissions the lambda with compensate for its condition.

 

[MG cup]

To a certain extent, how can it compensate if its chocked though?

My dads HKS mushroom filter needs cleaned yearly or it fails its MOT.

 

[Carbon-Rain]

I had the same problem with mine for the mot, turns out the testing station did not get the cat hot enough before the test. So a quick drive round at 50 in 4th solved the problem and she passed. I do have a 200cell sports cat not the standard one.

 

[James28]

Well my car is remapped using the RS Tuner.
I had been running it decat, but put the cat back in a week ago specifically for the MOT
I have bought a new pre cat lambda. Post cat only turns the light on so don't really need to bother with that one anyway do I?
I drove it for 10 mins prior to them doing the MOT up and down a junction on the dual carriageway,
they did it pretty much as soon as I dropped it off
I have a Ktec panel filter. I'll check it.

 

[kmorgan]

My car failed mot yesterday for exhaust emissions lambda reading after 2nd fast idle being outside specified limits (1.885!) Failed last year too but replaced one of the sensors and put a cleaner though it (think the one that is mentioned a few posts above) and it passed then (1.01) but failed this year. May try and do the same as last year if that doesnt work im guessing its a new exhaust for me! My exhaust is standard and rusty as hell although it has been wrapped and had all the holes filled haha.

Not too impressed that an 05 car is failing on emissions though!

 

[James28]

Replaced the front Lambda sensor.
Used my RS Tuner to check them. Rear lambda was definitely faulty as the reading didn't change at all. So I put the old front Lambda in the post cat hole.

Idle:

~2k revs: