NCT Emissions Fail (Again)

GE90

My 99 mazda 323 1.3 failed the nct retest on exhaust emissions.

Engine/Oil Temperature 100°C

Low idle (660 rpm) CO 0.41 vol%
HC 143 ppm

High Idle (2870 rpm) Lambda: 0.99
CO 0.35 vol% (Above 30% is a fail)
HC 112 ppm

Can anybody shed some light on what might be causing the problem. Do the results point to one particular issue?

Thanks.

George Dalton

Looks like a possible catalytic converter issue but impossible to say via the internet.

What did you do to the car in between the first test and retest?

How do the readings compare between the first test and retest?

GE90

Thanks George i appreciate your input.
Since the last test i have done a lot of work on the suspension but nothing on the emissions i was hoping she might pass the emissions the second time. I did however drive her quite hard to the test center as is evident by the high oil temperature.

Hear are the results of the previous test:

Engine/Oil Temperature: 81°C
Low idle (750 rpm)
CO 0.21 vol%
HC 205 ppm

High idle (3120 rpm)
Lambda: 1.01
CO 0.49 vol%
HC 195 ppm

Overall there was a improvement since the last test but not enough to pass.

George Dalton

A good fuel system cleaner might just get it scraped through under the 0.30% mark. Failing that I would say you are most likely looking at forking out for a new cat.

Try something like BG 44K if you can get your hands on it. Where are you located?

GE90

I am in Clare George. I will try the fuel cleaner and see how it goes.

George Dalton

A lot of fuel cleaners don't do very much in my experience so be careful. A few that do actually work are:

BG 44K as mentioned
Cataclean
Forte fuel injector cleaner
Wynns professional fuel system cleaner

An oil and filter change may also help if it hasn't been done recently.

GE90

Thanks george, Oil and filter was last changed in early January, about 4000 miles ago

breadman

Cat.converter needs replacing, those solvents dont work.I failed nct twice with that rubbish.Got cat. done for 180euro local in Dublin and passed straight away

Nissan doctor

breadman wrote: »

Cat.converter needs replacing, those solvents dont work.I failed nct twice with that rubbish.Got cat. done for 180euro local in Dublin and passed straight away

It depends entirely on your test results. If you had very high CO readings then no amount of treatments will fix it but in the case of the OP, they are only a tiny amount over, so a treatment may just scrape them under.

Obviously its not a permanent fix and the cat will likely need to replaced for any further NCT's.

dh0011

another good treatment is dieptane