Emissions

[colin mee]

Hello all.just had a call from the mot garage they day my emissions are just over. Anyone have any ideas how the bring them down.

[rev-erend]

New set of spark plugs.

Trim the co on the air flow meter.

[colin mee]

Done the plugs. How do I do the meter

[SLB]

You could try raising the idle a touch, particularly if you have a racier cam.

[rev-erend]

I think some airflow meters have a idle trim screw. What afm do you have?

Do you have a co2 meter?

[colin mee]

Will get a photo

[colin mee]

Can't,see a screw

[BlueWedgy]

If It's a V8 is it not the mixture screw. Sorry poor picture gleened off here (RIP), still helping folks out.
http://www.vintagemodelairplane.com/pages/Rover_Te...

And this about page 15....

http://www.vintagemodelairplane.com/pages/Download...

Edited by BlueWedgy on Wednesday 24th April 19:31

[Adrian@]

TBH, there is a reality check here ..take it to a different MOT station next time. A@

Edited by Adrian@ on Wednesday 24th April 19:39

[colin mee]

Think I will next time.only a few more mots

[rev-erend]

Also, if its failed an emissions test it could indicate that something is not right.

Some potential areas to investigate:

Plug leads
Dizzy cap and rotor arm
Fuel injectors
Fuel filter
Throttle position sensor
Air flow sensor issues
Wiring issues

Edited by rev-erend on Thursday 25th April 17:35

[Wedg1e]

I find turning the fuel pressure down a bit for the duration of the test helps... then wind it back up afterwards.
A standard 3.5 probably won't have an adjustable regulator though.

[mrzigazaga]

Adrian@ said:

TBH, there is a reality check here ..take it to a different MOT station next time. A@

Edited by Adrian@ on Wednesday 24th April 19:39

+1...or drive it about for 20 minutes before you take it there..

[RSTurboPaul]

mrzigazaga said:

Adrian@ said:

TBH, there is a reality check here ..take it to a different MOT station next time. A@

Edited by Adrian@ on Wednesday 24th April 19:39

+1...or drive it about for 20 minutes before you take it there..

Italian tune-up using decent fuel, arrive red-hot

[rev-erend]

What we're the values given to you for the fail.

From memory, I think co2 is a very generous 1% and is fairly easy to get under in a wedge but If you have an issue then it fails.

I also used to make sure I had changed the oil and filter before the test as every little helps.

[colin mee]

[mrzigazaga]

How old are your spark plugs? having the right plugs make a difference, my old 350i gradually began to overfuel but over a couple of years, I do recall Mr King taking the mixture down a tad on the AFM to the acceptable level.

[colin mee]

Plugs and leads are about 6 months.

[Wedg1e]

CO (not CO2!) on cars that age is 3.5% as shown above; I used to have a Gunsons gas analyser and checked mine pre-MOT. However after some years where the car seemed to pass without needing any adjustment I realised I hadn't seen the analyser in a long time and despite a major ransack it has failed to appear. I suspect I loaned it to a forum member who has omitted to return it, as nobody else I know would have had any need of it. Chances of them spotting this reminder: slim

Crankcase breathers and the like can also be a cause of high hydrocarbons (as in the OP's case), worth a good washout/ blow-through as appropriate.

[Englishman]

It has failed on HC, not CO from the picture. Usually means too much fuel in the exhaust. Was the engine hot? Wedges do over-fuel when cold. Otherwise I would make sure you have a spark at all plugs as if one or more plug is not firing that can cause the issue too.