CO adjustment only affect idle on a 3.2?

dimeified · 09-13-2008, 06:14 PM

My carrera has sat for half the year and i havnt had too much time to mess with it except to start it up and let it idle to keep the fluids moving. I am ready to dive back into it, so i ordered a gas analyzer from innovative, the LM-1. I got the exhaust to fluctuate around the 14.7 to 1 and lambda 1 ratio by use of the 3mm allen screw under the afm.

I've tried fuel injector cleaner and dry gas in the tank, but i can't help the rough idle or the hesitation on wide open throttle. The problem has cleared up a little since i've been driving it non stop but the issue is still there. My uncle has a machine to clean injectors, so i may visit him next week.

but my question is, does that CO adjustment affect throttle too? I may try to lean out the mixture if that is the case.

scarceller · scarceller's Garage

The CO adjustment screw on the AirFlowMeter bypasses air around the barn door within the AFM. So if you turn the screw out (counterclockwise) you allow more air to bypass around the door and thus the door closes some and the 0-5v output voltage from the AFM goes down. If you screw it in you close off bypass air and the door opens more and the voltage goes up. So that's the theory.

From this theory I can tell you that if you adjust the screw it has effects across the entire RPM range. So if you wish to richen the mixture simply screw it in (less air bypassed) and the mixture gets slightly richer at idle and also off idle.

But I don't think that this is your issue unless the carbon track (resistor track) inside the AFM is bad, it's easy to test this track, read my paper here:
http://members.cox.net/widebody/AFM/AFM3.2LCalibration.doc
it has a section on testing the AFM output voltage, the idea is that as the door swings open the voltage must track very cleanly from 0-5v it should not have any spikes. If it does you have a bad/worn carbon track and this will result in poor drivability.

Hope that helps.

stlrj · 01-20-2009, 02:52 PM

Quote:

Originally Posted by dimeified

I've tried fuel injector cleaner and dry gas in the tank, but i can't help the rough idle or the hesitation on wide open throttle. The problem has cleared up a little since i've been driving it non stop but the issue is still there.

Before you do anything, have you performed an ignition tune up?