RPM goes up and down while adjusting idle
 

Hi All

Since I bought my car, the idle were set to 1100 RPM.
I was trying to lower the RPM but when I reach 850 RPM the engine starts working weired...the RPM goes up and then down, up and down...when I set it to 900 RPM it is stable but when I open my A/C the RPM drops and then rises, drops and rises (the A/C air switch is working ok).
Now, my CO levels are high. they about 6-7% instead of 1.5% but I thought that it couldnt be a problem to lower the RPM to about 750 RPM and later adjust the CO levels since I need the CO meter and I dont have it right now.

What do you think it indicates when the RPM goes up and then down all the time under certain RPM?

Could it be because of the high CO levels?
I know that my fuel pressure is good and all other electronic devices are good.

Any ideas?

I think your on the right path. Adjust your A/F (large screw), but make sure you document what you did (ie: 1/8 turn clockwise, etc). CIS adjustments are very fine and it takes a lot of practice to get right.

Thanks but how can I adjust it correctly if I cant make the RPM lower then 850??? this drives me insane!
I think that first I should make the RPM high...even 1500. Then, adjust the CO level until I reach ~1.5% and when I am at 1.5% lower the engine RPM to 750 RPM

Is it the right way? I just wonder if the RPM rises and then drops all the time in about 850 RPM means something?