Posted by Peter Florance on September 09, 1998 at 22:18:18:
In Reply to: Idle speed & mixture posted by Cliff Robb on September 09, 1998 at 11:04:39:
: Ok, so I'm playing around with the idle speed screw on the throttle body last night. I like it to idle just a tick under 1000 rpm, & it seems like I need to tweek it a little every few weeks. I am reasonably sure I have no vacuum leaks, and the car does idle smoothly. A couple questions: Someone recently mentioned if the idle speed increases or decreases when you pump the brake pedal, the mixture may be rich or lean. I quickly scanned the postings & could not find the topic. Could whoever posted it kindly tell me again? Also, my car idles smooth, but over the last few months, I have noticed it hunting up & down about 50 rpm like the O2 sensor is making corrections. I thought the O2 sensor was out of the loop at idle, what gives? If I unplug the sensor-rock steady idle. Maybe the mixture is off. as I said, it speeds up when I pump the brake. On the mixture srew on the AFM, do you tighten to lean & loosen to richen? I was thinking of experimenting a little, making note of the original setting. So let's hear it, what do you all think?
I guess it was me....
I think what I said was:
If you pump the brakes and it idles faster/smoother then the engine is rich and it 'needed' the additional air.
If you pump brakes and it idles worse, then the mixture's either correct or lean. And if it idles worse when you pump brake but better when you inject in a little propane gas, THEN you can say it's too lean.
Did I say that right.....?
Peter