How Lean is Too Lean? 3.0 CIS

[scotricker]

For the past few days, when I get home, I adjust the mixture and idle to be just a little bit leaner. I don't want to make a big change all at once.

I'm trying to stop the idle bounce during cold idling in the morning.

So, every next day morning, it runs and idles a little bit better.

How will I know when I get too lean? It won't run? Is that it?

[Peter Zimmermann]

You should NEVER adjust the fuel mixture without taking an exhaust sample with a calibrated CO% machine!!! Right now you're tinkering with possible detonation, a possible blown airbox, and other issues.

BTW, on mornings when the ambient temp is about 50F or lower, a little idle fluctuation is a good thing. It means that your warm-up regulator is set slightly on the rich side (which will protect your airbox), but has virtually nothing to do with operating temp mixture.

[Gogar]

+1 I agree with Peter, Idle bounce on cold startup is NOT specifically caused by 'too rich.' You have to make sure you don't have any vacuum leaks, and that your CIS components like the WUR and AAR and Cold Start Valve are operating properly. Simply adjusting the mixture screw without checking everything is a bad bad bad idea.

Set the mixture screw when the car is warm and idling. That's all. Then, everytime you change something in the fuel system or intake, check it again.

[Joe Bob]

Idle bounce....leaky induction that seals up when warm.

[81 SC Ray]

Don't just mess with the mixture screw based on Zen. I did this and ended up having to bring it to a shop. They put the sniffer on it and set it properly. I still get crap gas mileage, but, it runs like a champ.

[scotricker]

Well now I'm thinking I should richen it back to where it was.. Or what?