Why does it fail on emmissions, even after installing 2 new

[kamalsrana]

Hello there,

Hows it going, looks like you've all been busy while I was away.

I am back now and wanted to et you all know that my MOT failed on the LC 100 because of emmissions.

I had a new sensor installed last year and 2 new cats, but this year it failed again.

Is it because I did not thrash the hell out of it on the highway or is there something I need to do before going for MOT?

All advice will be looked at closely.

Thanks in advance.
Kama.

 

[Jon Wildsmith]

Re: Why does it fail on emmissions, even after installing 2

you don't say what sensor was replaced? the air flow sensor near the air filter and the o2 sensors in the exhaust are probably the main things to look at and you might also consider cleaning the throttle body and butterfly if you haven't already.

I put OEM O2 sensors in mine about 15k miles ago and until about a week ago was chasing a lean condition at some RPM for a few months and mistakenly discounted the O2 sensors because of their age. Fitted some NTK O2 sensors last Friday and problem solved so don't assume OEM sensors will last

 

[Rob Voerman]

Re: Why does it fail on emmissions, even after installing 2

check for leaks in inter-cooler line, mine also failed and the MOT bloke tightened the clamp

 

[kamalsrana]

Re: Why does it fail on emmissions, even after installing 2

Dear chaps,

Thanks for the info, I will look into it and get back to you all.

 

[Beau]

Re: Why does it fail on emmissions, even after installing 2

It's worth doing a good run with it as well to clear out all the carbon from the engine and exhaust.

 

[kamalsrana]

Re: Why does it fail on emmissions, even after installing 2

Hi, I remember that I had changed the lambda sensor as one was showing as running rich and the other one lean.

The problem was the one running lean was alright, the other sensor that was running rich was doing so as it was the faulty one.

After replacing faulty sensor, it was still running rich, so I was told to replace the cats as they seemed to be the culprits. After spending more than a mortgage I changed the cats and it passed last year.

This year, I have driven regularly on the roads and it failed .

Fortunately for me the MOT guy passed it, I am just worried about the next time as I cannot keep forking out for cats etc.

So I am OK for now.

 

[Jon Wildsmith]

Re: Why does it fail on emmissions, even after installing 2

Did they reset the ECU (disconnect the battery for a bit) to reset the long term fuel trims last year after changing the O2 (lambda) sensor? It takes quite a lot of running time to bring the fuel trims back down so the best thing is to just reset them and start again.

I would suspect either the MAF or the primary O2 sensors I can't see it being the cats not this time or last time tbh.

 

[kamalsrana]

Re: Why does it fail on emmissions, even after installing 2

OK mate, I will give that a try.

So I will disconnect the battary and then reconnect after 10mins or so.

Cheers.

 

[nathanrobo]

Re: Why does it fail on emmissions, even after installing 2

Would it make any difference to clean out the EGR system?

 

[Jon Wildsmith]

Re: Why does it fail on emmissions, even after installing 2

It's a petrol, no EGR

 

[nathanrobo]

Re: Why does it fail on emmissions, even after installing 2

Opps!