On a 1993 90 CS Quattro early style MAF sensor has screw type adjuster on top left. Is there a way to adjust the CO% with out a CO% meter. Car seems to be running rich. Output of O2 sensor is aroung .9 volts.

Regards,
Rick

CO is measured from 2 tube taps which run off the exhaust manifolds before the gasses reach the cat.

On the older Audi's with CIS or CIS-E, one could adjust the CO using a voltmeter, connected in series to the sensor on the fuel pressure head.

Your car, has a different ECU & Fuel management system. It can be adjusted using the 1551 or VAG-COM software. I dont know of a proceedure which allows otherwise?

You might try turning the adjuster screw a slight one direction or another and testing. If too much, turn it the other way.

1990 80 [199,000+mi. almost there]
Well, my car had tis problem. Loud and powerful exhaust at idle, poor gas mileage, and the running rich code. Well no one knew how to fix it. That includes everyone on this board, one audi dealership who serviced it and one that I stopped by to ask, a euro car specialist, and a pleathera [sp.] of other mechanics that did not know. All I got where bull answers that were not the problem.
Eventually I figure it has to do with the ilde adjustment and i start makeing some adjust ments. The bentley says that timeing, idle and CO have to be adjusted together. Well I do not like useing guess work and do not have a CO tester so I will have to set it the best I can. Has anyone ever done this type of tune up on one of these motronic cars? The idle speed cant be adjusted can the ignition timing?
Can the O2 sensor be used to aproximate on the cis motronic?

Timing is adjusted via the ignition distributor.

CO is adjusted via the fuel pressure head CO adjust.

It has a differential pressure reg, and thats where you attach (in "series") a voltmeter to tune.

Done it dozens of times.

However your problem sounds to be a bad fuel pressure head. Very common on high mileage auto such as your 199,000+ Audi! Especially if soooooooooooooooooooooooooo many people cant fix it.

Bring it by my house, and I'll let you know in about 10 minutes exactly whats wrong with it.

Troubleshooting here via this forum is always a
"guessing game".

Much more better to troubleshoot with car sitting in front of you. Better results usually occur too!

Do you believe that a company in georgia sells the for $129, its just a couple wires.