carbon monoxide emissions co MOT

[nks350i]

Hi there

Fail MOT last week on a few things, two of which are fixed, however also on co at 4.51% (last year it was 2.5%) with a limit of 3.5%. Borrowed a co gas meter (Gunson gastester) and trying to get to grips with what happens. Looked at this www.tvrwedgepages.co.uk/maint_fuel_injection.pdf page 21. My adjustment was at 8.75 turns from fully CW - a lot more that approximate setting of 2.5. At 2.5 the co emissions go high around 6%, taking it further ACW doesn't seem to have much differance (turn it a bit it goes down turn some more it goes up!) from my reading at 8.75 turns ACW. I'm reading it around 3.0% (when I left it!).

Anyone got experience of the ajustment / expectd co levels at idle (idles at 700 RPM),

Car is 350i 1987 with Lucas 2AM air flow meter

Thanks Nigel

[Danny Hoffman]

Hi,

What fuel are you using? I usually fill up with with 95RON prior to the MOT instead of 98RON which I normally use. This year I forgot and for the first time ever I got an advisory than my CO was high

Danny

[nks350i]

using 95 RON

[mk2 24v]

What state are the spark plugs in?
Had a Range Rover in at wotk recently, and that failed on emissions (not even close to the limits of getting through!)
Just a quick clean up and regapping the plugs had it sail through though

Have you got the HC reading as well from the test?

[chj]

You could try increasing the idle speed for the purposes of passing the mot - I would have thought the emissions would be a lot lower at around 1100/1200rpm?

Chris

[pasogrande]

Nigel,

I had work done on my 280i exhausts and failed our version of the MoT (We no longer have the testing as it was thrown out when we got a Republican governor!) The problem was that the single catalytic converter was moved from under the oil sump. With two exhausts the new cats were moved a long way back. The cats only work if they get really hot, ie not too far from the engine.

If your car has a cat setup, and if the location is changed, this may be of interest.

Wilf.

[adam quantrill]

Your idle is too low - set it to 850 to 900.

You should be able to set to 1% easily.

[nks350i]

thanks for the replies. HC is 289ppm, was thinking about increasing idle but wasn't sure what effect it would have on co - I will give that a go tomorrow.

[utternutter]

I've just set mine ready for the mot but have you done the ignition timing ???? 8 degrees BTDC with vacum removed at 1000 rpm, done my emissions with gunsons again at 1000 rpm and ideal around 2% at that speed and don't forget to rev the engine every 3 mins and let settle before adjusting again, the engine tends build up co2 while ildleing for a length of time giving false reading. after, when satisfied adjust idle back to 800-900 rpm, take your time when doing it, took me 21/2 hours + but got it spot on.

[wild rover]

Whats the fuel pressure like at idle should be 38psi.