Emissions - gas analysis

[tha881]

So I've recently had the car mot'd and the emissions results are as follows

CO level 3.82%
HC level 455ppm
Co2 11.42%
O2 1.44%
Oil temp 28 degrees c

Car runs nicely sometimes drops a bit above 500rpm when returning to idle.

I have noticed the cap on the afm screw is missing so is this a symptom of someone adjusting it in the past?

Any advice would be appreciated

[Satan]

I had the injectors cleaned and the MOT guy did say that the emissions where nice and low, does seem to be "hunting" a little when on idle but i need to get the idle adjusted.

What engine do you have in your car as mine is a 2.5?

[paultv]

Your CO is a bit high - UK is max 3.5 for a pass and the M20 should be between 0.8 and 1.2 - 1.0 being optimal. If your idle mixture on the AFM has been messed with then you need to set it with a gas tester but AFTER you've made sure everything else is in good shape, no air leaks - cleaned injectors, air filter, fuel filter, plugs and distributor cap and rotor, also check fuel pressure - in other words the beast is running as it should, then set the idle CO and put a new plug in the mixture tweaker.

I've probably missed some of the to do things to get this right, anyone?

HC on my m20B25 is 131ppm, pass being 1200

and I think CO2 should be 12% ( or is it 14% can't remember ) so that's pretty OK

Paul

[tha881]

Thanks I should have said its a standard m20b25.

Injectors have been refurbished, its been serviced recently including valve clearances, had new fuel filter, fpr, air filter, rubber elbow, tps etc

Only bits I havnt done are intake manifold gaskets and distributor cap and rotor arm

[paultv]

so then it sounds like it's running rich when idling - hows your exhaust outlets, black and sooty or clean ?

Paul

[Satan]

so then it sounds like it's running rich when idling - hows your exhaust outlets, black and sooty or clean ?

Paul

Thats a bit personal Paul........

[paultv]

We're all intimate friends on here! How's your pipe?

Paul

[martauto]

Mart.

[Satan]

Mart.

I assume you've never met Paul and his family.......

[Brianmoooore]

Maybe the CO adjustment has been 'got at' in the past, as you suggest, making the mixture richer to compensate for air leaks and badly performing injectors, so now, with serviced injectors, it will tend to be rich, which is what your results infer.
If you're sure there are no inlet air leaks, get it back on the gas tester, and tweak it for 1% CO, or slightly less.

[tha881]

I agree Brian. Thanks for the advice. I may do the intake gaskets before i put it back on the tester just so i know there is no leaks at all. I will also be marking the screw so it can be put back if need be, even though it has probably been tampered with.

[Satan]

Checked my car today, if I lean on the air filter the car cuts out noticed a split in the rubber boot so have taped it up for now before ordering a replacement part.