Adjusting the CO2 mix- default setting?
 

Just want to make sure my car is not running rich or lean!.
The "trusty" mechanic left the car adjusted so it was right with the O2 sensor unplugged. Because he said the leaky valve was making the fuel effect the O2 sensor thus leaning out the engine!!!!!
Poppycock!
I removed the O2 sensor cleaned it and replaced it and the car runs fine!.
So.... How many turns each way should the allen screw be turned to be 'normal' or is this a job I should leave to the experts?
Thanks Guys
Ben

Ben,

Be careful playing with this yourself. It really needs to be adjusted with an exhaust gas analyzer to get it right. With what you've been through, I'd hate to see you back in the soup again!

Good luck,
Mike 94 C2 cab

Woops!? I must have been tired, I thought it said, 83ragtop. Nevermind...

[This message has been edited by ckrause (edited 07-10-2001).]

A couple of people on this board have had luck about 10 turns out. Mine was 8.5 turns out. Don't know if it's perfect but feels good to me.

Joseph
'86 T-look

Not too worried about smog test etc, as in Florida, but want to assure not running too lean!.
Joseph, did you wind yours all the way in and then wind out 8.5 turns?
rgds Ben

Why does your Motronic AFM need adjusting? This is not a part that normally needs "adjustment."

Or are you talking about a CIS car? That would be different.

I believe the PO adjusted the CO2 from factory setting. The P-mechanic in an attempt to stop irregular idling -he thought was caused by a leaking exhaust valve, then disconnected the O2 sensor and adjusted the CO2 mixture to attempt to get the car running right!.
I know this is all wrong!.
But after collecting the car from the mechanic, I cleaned the O2 sensor with electrical cleaner and replaced it. The revs then ran stable. But now i guess the CO2 screw needs to be returned to the default setting!.
I will try screwing it in completely tomorrow and then unwind it 8.5-10 turns until it runs right?
any other comments appreciated

uh... guys?

are we all sure that one man's '10 turns out' is going to result in the exact same mixture as the next guys '10 turns out'? is this really as precise an estimate as we are implying?

ben: i'm not sure you can target your car's optimum mixture for certain without an exhaust gas analyzer. but, hey, i'm no motronic expert, either. i just want you to be careful with your car in light of the trauma you just went through!!! i don't think this is a trivial adjustment. :-)

how about one of you mixture adjustment experts setting us straight on the facts here?

------------------
Adam Nitti
ajnitti@mindspring.com
www.adamnitti.com
'85 911 Carrera Coupe
PCA member, Peachstate region

Yes Ben, that's what I did. I also didn't believe one man's 10 turns.... Anyways I noticed a big difference. It was 8.5, pretty close. Probably fine tune with gas analyzer later. Start at 5 turns out with a trip around block at each turn. I don't think factory sets at performance optimum. They have other priorities as well to balance. Probably best performance for cleanest air and best fuel economy. I also might be wrong. My credentials are limited.

Joseph
'86 T-look

Thanks for the concern adam! http://www.pelicanparts.com/ultimate/smile.gif
But the thing is the P mechanic ****ed around with the screw and so i am sure it is not correct now!. But the car runs okay.
I will try to adjust and as you say, have it tested once near a trustworthy dealer/garage.
rgds Ben

As far as I can tell, P factory tunned them around 5 turns. My 85 had not ever been adjusted. The factory had it 5 turns out, way rich, soggie bottom end, rough idle.
I went by Joe Garcia recomendations, around 9 to 10 turns out works fine. I have been running like this for 2 years, 40,000 miles.
The screw basically passes air around the barn door. Everyone seems to be a little afraid with this adjusment, heck the dme knows when the head temp is going up, and will make changes, we also have a o2 sensor.
Keep turning the screw out till it idles good, and has a crisp snappie bottom end.
DRD
Darren

Just checked it,
screwed it 4.5 turns in to 'stop'.
Then screwed it 5 turns out, she ran fine, have now tried it total 8 truns out and will drive it around like that for a while.
Does more than 5 turns 'lean it out' and how do you know if she is running lean or rich (sorry but I am a beginner at this)
thanks for the extra info DRD will try it with 8 and se how it goes!.
Thanks all
rgds Ben http://www.pelicanparts.com/ultimate/biggrin.gif
PS now going for a long drive with top down- day off!!!!
Wooooo Hoooo! http://www.pelicanparts.com/ultimate/smile.gif

I've done this adjustment too. My '87 is now at 7 1/2 turns out, was at about 3. Done this before on my old 75 VW, same set-up. This really affects low to mid throttle range, not top end, full open. Does run better around town, but it won't meet emissions standards. I think the CO will be too high.

Ben, yes the more turns you go out, the leaner the mixture. My tail pipe is a golden brown color, you can also pull a spark plug and the color of the spark plug will tell you what is going on. Also there is a position switch on the dme brain, to richen the mixture on the mapping by 3%. Kinda sounds weird, but I richened the dme 3% and then leaned out the co2 mixture untill it got nice and crispie.
DRD
Darren