extreme high Co2...up to 12%

[mstar]

Hi, I have a problem with the Dutch APK (is like the UK MOT) testing and approval, they Co2 is too high and they said to be able to sort it out and fix it...but they couldn't. So I took it home.
It seems to have too rich mixture and bad combustion although it does not run bad. Spark plugs were black but seems not to burn oil.
ECU was chipped with an unknown chip and that's why I was searching for an stock chip in my other thread...installed it but no improvement, exactly the same read out. They renewed the blue temp sensor and CO pot, it does not get better and the car approval was rejected
What can be the problem: fuel pressure reg., injectors, lambda, knocksensor, idle/full throttle switches??

I can hear the idle/full throttle switches make click sound but did not measure them yet.
The read out at idle showed a temp of 93 degree celcius, injection time at idle 1,5 to 2Msec, lambda voltage 0,16v (if I remember good)

Can it be a ground problem that causes the injectors not to close completely (bad/worn ECU relay)?
Can I clean the injectors my self?


Thanks for the help
Matthieu

[PeteG40]

have you adjusted the co pot? what value is it set to?

[mstar]

Hey PeteG40, this mechanic tried to adjust it but has no effect at all, I don't know the resistance value. The CO pot is new.
I read on this forum starting values of 550, 600~650ohm's, I will put it back to that and start searching with testing wires, connectors, grounding etc...

Is there a possibility that the MAP sensor in the ECU is faulty? Although no faults were shown when the ECU was connected to the VAG like device, all reading looked oke.

Is the lambda voltage at idle correct? Only 0,16volt.

[G-spot]

Only a quick suggestion, I had a similar problem on MOT, but it was down to the throttle  valve not being fully closed(hence the Throttle Posistion Sensor not being at zero or the idle micro-switch not functioning properly) and therefore idle bypass screw not doing it's job properly.
Ensure there is plenty of slack in your throttle cable, and the throttle stop screw is allowing the butterfly to close fully, then adjust your idle using the bypass air bleed screw on the back of the throttle body.  Mine came straight into specifications after doing this.  Do check CO pot is correct and ensure all your other tubes are fully servicable(ie no air leaks)

[polo classic]

High CO (5-6-7+++) usually indicate faulty lambda and/exhaust leak

[mstar]

Fnally got my G40 approved for the Dutch APK (is like the UK MOT), CO is now perfect.
What I did is the following:
- cleaned the throttle body inside and checked the switches. Was incredibly dirty.
- cleaned the whole air intake starting at the airfilter, intercooler and all piping, inside here was a grey colored greasy layer
- have the injectors cleaned and replaced one.
- Finally replaced the lambda sensor, at a rich mixture the output was only 0,16volt (this low voltage should indicate a lean mixture) So Polo classic was right pointing a the lambda. thanks for that.
Now the CO is 0,04% at idle, it starts immediate and nicely.

Because of all this the adjustment of the CO pot and air bleed screw is now probably wrong, the rev's jump between 900 and 1000 rpm.
What is the best way to adjust the CO pot and the air bleed screw?
Thanks.

[mstar]

Thanks Rae.
My worry is that it runs lean now as last night when driving it hasitates a bit at low rev's and then accelerates quick.

550, 600~650ohm's is as I understand it a starting value when adjusting it, but what value it actually will have when properly adjusted at the end? (knowing not all engines will have the same setting, but they should within a limited range)

[hayesey]

650ohms is a good base setting for it.  If it passed the emissions tests then it's probably right as it is.  There is no "value it'll have after adjusting to suit", the whole point of it being adjustable is that each engine will have a different value.  Although I wouldn't expect it to vary TOO much from around 650ohms.  I've seen one set to like 2.25KOhms before though which someone set to pass an MOT emissions test here in the UK.