Has your MX failed the NCT? And why? ..

[mrges]

And............................................. failed!!!!

Emissions. "Everything is fine..... except your emissions. They are through the roof"

Low Idle CO 10.66vol% (Above 3.5% Fail)



ARSE
FECK

[mrges]

Searched through this topic - and see other folk have failed for same thing.

Anyone shed any light on what causes (caused) this..... and more importantly how to fix it?


Thanks,
Graham.

[Steve]

I'd start with these :
Check your intake from airflow meter onwards for leaks/splits,
check voltage of O2 sensor,
check thermostat isn't sticking open,
check temp sensor at the back of the head is working.

[mrges]

Hi Steve - thanks for getting back to me. Will try start finding those bits and getting the checks later. A new thermostat was fitted last week (so I'm guessing I can rule that one out).

I've had the car of the road since November - could that influence things in any way? (Oil changed on Monday of this week, and although the NCT Centre is about 15 minutes away i left an hour early and drove the long way to it (arriving 5 mins before appointment). Could the cat be another potential cause?

Thanks.
G

[Pops]

Don't know if yours is 1.6 or 1.8 but my 1.6 had a split in the rubber intake pipe, hard to spot without separating the ridges in the pipe, made a world of difference when replaced. Pics on this thread viewtopic.php?f=8&t=8202

[mrges]

Thanks for that.... hoping to go explore soon!

[mrges]

Folks.... anyone got any further ideas on how to reduce the emissions???!!!! Failed again on same thing. To date the following has been done:
Replaced thermostat
Replaced Temperature sensor
Replaced airflow meter
No splits (that can be detected) in pipework
(changed the oil)
There is a CAT fitted (which I'm told is "ok")

I'm STUMPED (and mightily pi55ed off. Was really hoping to drive up to Kirkistown in the car this weekend - but that ain'r going to happen now).

Car was left in with a guy who "does emissions" in Tullamore, and his suggestion is that the ECU needs replacing. Could this be the culprit? (if so, is this difficult to replace? Is it expensive to replace?)

Two other things:
1. There is a drop in revs at idle - sorta idles unevenly (it feels like it might cut out - but never has)

2. (And probably a VERY stupid question) .... are the emissions levels the same for a Eunos as for a MX5? The car is a MK1 (1993) 1.6 Eunos (BUT in the log book it's listed as a MX5).


Reason given for failure is:
Low Idle CO 10.66vol% (Above 3.5% Fail)



Any help greatly appreciated.

Thanks again,

Graham

[Pops]

Was the temperature sensor that was replaced the one at the thermostat housing or the one at the rear of the engine?
The one at the rear is the one for the emissions.
Also I'd say the base idle isn't set properly
https://m.youtube.com/watch?v=PVi2uaxAwnU

[Pops]

Guy has a very long thread on another forum with the same problem, he too tried everything, turned out to be clogged injectors, fixed with cleaner.
Mines a 93 1.6 eunos as well but it is classed as a Mazda other on the NCT cert , hopefully the pictures will load so you can compare with your test

IMG_1997.JPG

IMG_1996.JPG

IMG_2001.JPG

Also a pic of the diagnostic led from Maplin, I think it cost about €2

[Pops]

Found the link http://www.mx5nutz.com/forum/index.php?showtopic=94223

[mrges]

Thanks very much for the info..... really appreciate it. Will explore further. It's a real pain in the ass. Have some Redex here - but haven't used it yet.

BTW, I've had the thermostat at the front, and also the one at the rear of the engine, replaced. ANd I didn't mention this earlier (I forgot!) - there is a Jackson Racing Cool Air Induction kit fitted in place of the regular box.

Thanks again.

Graham

[Pops]

Might be no harm to check the wiring connections on the intake as well, it's possible the joins may not be good

[93 Mk1]

What condition are the HT leads in ?
My current '5 failed for emissions a few years back. I couldn't believe it but it turned out to be a cracked block !! Who'd have thought ?
As for a system cleaner, I swear by Dipetane. It works great for both petrol and diesel motors. I usually mix it much stronger than the
recommnded dosage on the bottle i.e. half the bottle to half or 3/4 full tank.

[mrges]

Thanks for the suggestions.... and hopefully it's not a cracked block!!!!

Will add the ideas to the list of things to check! (and I also forgot to mention earlier, plugs and HT leads replaced earlier this year).


It's getting close to wanting to walk away from it at this stage!

[mrges]

NCT.jpg

Well, after what seems like a mountain of trials and tribulations....... NCT finally passed today! Feeling VERY pleased (and relieved). Poured in a dose of Redex to about a quarter tank of fuel as a last gasp attempt before heading off for the test, and drove for about 40 minutes (in a rather "spirited" manner) to the testing centre.

At last!


G