High Co Emission Failure

[GAPAUTO]

Hi Guys,

I went for a emission test today and it was failing on idle with a high CO value. I'm doubting that i have messed up with the idle mixture and want to get your inputs as well.

I'm attaching my existing (Passed) results sheet and the new (Failed) result sheet.

Failed

Passed

In the failed report i think my 2500 RPM seems to be ok other than the indication of low lambda which might be caused by the my airfiler which i will replace before my second try. Please give me your inputs

GAP.

Edited July 5, 2014 by GAPAUTO

[Rumesh88]

What is your car? Carb or EFI? Though you got through on your second attempt you still have high CO levels which is most likely caused by a rich mixture.

[GAPAUTO]

What is your car? Carb or EFI? Though you got through on your second attempt you still have high CO levels which is most likely caused by a rich mixture.

Its a Carb on 4G12 Lancer. Well the Pass Image is my last year result. Still i didn't went for the second attempt.

[Rumesh88]

Its a Carb on 4G12 Lancer. Well the Pass Image is my last year result. Still i didn't went for the second attempt.

Not a big deal then. If the fuel level inside the carb is at the middle mark, all you may need is a clean up of your carb by spraying carb cleaner down the throttle body. Is your idle stable (no stalling and smooth)? If not you may need a readjustment of idle and the mix. Who is going to do it BTW?

[GAPAUTO]

Not a big deal then. If the fuel level inside the carb is at the middle mark, all you may need is a clean up of your carb by spraying carb cleaner down the throttle body. Is your idle stable (no stalling and smooth)? If not you may need a readjustment of idle and the mix. Who is going to do it BTW?

Well i cleaned up the Carb few weeks ago and fix a part load idle issue as well with the help i got from you on pin pointing the problem. But i think i didn't set the idle mixture after the second round of cleaning. I had a small hikup kind a stumble in idle which i think cause by running rich. Had some carbon around the ring of the spark plugs as well, but plugs were not fouled. I re adjusted the idle mixture today evening and found out i was running idle without event the idle speed adjuster was not even touching the throttle arm .

What i did was increase the idle speed, and then started leaning the mixture until the engine run rough. Step back until the roughness stop and Step back less than a quarter turn. Then readjusted the idle speed. This is something i used to do with my old VW Bug which i read from it's manual.

[Rumesh88]

Well i cleaned up the Carb few weeks ago and fix a part load idle issue as well with the help i got from you on pin pointing the problem. But i think i didn't set the idle mixture after the second round of cleaning. I had a small hikup kind a stumble in idle which i think cause by running rich. Had some carbon around the ring of the spark plugs as well, but plugs were not fouled. I re adjusted the idle mixture today evening and found out i was running idle without event the idle speed adjuster was not even touching the throttle arm .

..and I must have sounded bl**dy stupid when I asked what your car was . I seem to have occasional bouts of amnesia.

Well if the car was idling without the idle adjuster touching the throttle mechanism, it must have been due to one or more of the following things.

1. Accelerator cable pre-play (cable slack) is not set properly.

2. AC idle up dash pot adjustment (if equipped) is set at the wrong point.

3. Throttle flap is not closing properly.

Check these and get them corrected if necessary before you set the idle. Also see if the PCV tube (running from the middle of the valve cover on the intake side to intake manifold) is clean.

[GAPAUTO]

..and I must have sounded bl**dy stupid when I asked what your car was . I seem to have occasional bouts of amnesia.

Well if the car was idling without the idle adjuster touching the throttle mechanism, it must have been due to one or more of the following things.

1. Accelerator cable pre-play (cable slack) is not set properly.

2. AC idle up dash pot adjustment (if equipped) is set at the wrong point.

3. Throttle flap is not closing properly.

Check these and get them corrected if necessary before you set the idle. Also see if the PCV tube (running from the middle of the valve cover on the intake side to intake manifold) is clean.

I checked the cable slack which didn't had any problem, actually it has plenty of slack which i think i need to replace the cable soon because the adjuster is in its max . The AC idle up unit is custom unit which was fabricated using a diaphragm since this model didn't came with a original AC. So the idle up is clearly visible and a simple one which i did make sure it didn't had any thing to do with idle. Well the throttle flap seems to be seating when i took the carb out and clean few weeks back. After last evening idle tuning now i need to keep the idle speed adjuster screwed in a bit to have the required amount of idle speed. So probably i was running rich which i guess the reason the idle was not really smooth. And i think probably my timing is ok (Not advanced) from the HC levels in the failed report image. Any more thoughts ?

[Rumesh88]

Check the air-bleed of the emulsifying tube. If you can approach it from the top use a thin copper strand from a flexible wire to make sure that it is not clogged up. Take care not to drop any debris inside or i you do you have to open the carb from the top to clean the tube.