Failing emissions test - help!!

[Mark W]

Hi all.

My Rocket with a 1.8L Zetec failed the emissions test. Results at 3000 rpm were:

CO2 - 15%
CO - 0%
O2 - 0%
Hexane - 10 ppm
NOx - 116 ppm (FAIL - should be sub 20)
AFR - 14.73
LDA - 1.000

The ECU is standard and I have a Euro 5 catalytic converter in same place as old Ford converter.

Does anyone have any ideas?

Cheers, Mark

[deanohonda]

what temp was the engine running at ?
nox is produce when exhurst temps get to heigh
the job of an EGR valve is to reduce this
Had it been idleing for a while ?

[Mark W]

Hi.

The engine was hot, water temp at radiator 80-85 degrees.

The after market Cat (Euro 5) is noticeably smaller than the Ford one it replaced - could this be it?

[Stiggy]

Before you go spending money on a replacement oxygen sensor or EGR valve I would spray soapy water on all exhaust joints whilst pressurised, maybe use a vac on blow mode. A small leak can distort the readings. Maybe you have a vac leak causing weak mixture which can cause high combustion gas temp and increased Nitrogen Oxide.

[Stiggy]

here is a check list;
www.discountconverter.com/catalytic_converters_news/news_page.cfm?Key=catalytic_converter-&News=98

[deanohonda]

I would have gone for a air leak but lamda seems bang on the money
Would also expect lean fuel codes in pcm
Inlet air leak can be picked very easy spraying brake cleaner round all gaskets and joints engine revs will increase shield air filter so not to get an incorrect result
CATION DO NOT SPRAY ON HT LEADS COIL OR HOT MANIFOLD

[Mark W]

I spoke with several exhaust specialists today who all seemed to agree that the catalytic converter was too small. At idle (low flow rate) the system worked fine. NOx was 2-3 ppm. At 3000rpm (hi flow rates) NOx was 116 ppm - basically the cat wasn't doing anything. They've recommended a bigger cat and a new O2 sensor.

Thanks for all the advice - I discussed most of the ideas presented in this forum with the exhaust specialists.

Cheers!!!

[Mark W]

Passed!!! We changed the cat from a Euro4 200cpi cat, to a Euro5 400cpi cat about 60mm longer.

The NOx at 3000rpm fell from 116ppm to 0ppm against a target of <20.

All paperwork is with the engineer to submit to our DoT. Now just to wait.