Idle fuel mixture setting

[Jonathan R. Lusky]

Bohdan.L.Bodnar at att.com writes:
> Idle actually runs richer than 14.7:1.  There are several reasons for
> this (such as longer exhaust scavanging time at idle than off idle).  I
> also know that some engines which do not use heated oxygen sensors run
> open loop at idle;  this is because the O2 sensor will cool off and present
> incorrect readings to the computer which will then cause the engine to
> "hunt" as the air/fuel mixture varies wildly.
 
Whoa, be careful with the blanket statements.  I don't know about Fords, but
GM stuff DEFINATELY tries to run closed loop at 14.7:1 at idle.  I think
your statment applies more to earlier attempts at closed loop fuel
control than it does to modern systems.  From an emissions standpoint,
you'd want to be lean if anything at idle.

-- 
Jonathan R. Lusky  --  lusky at knuth.mtsu.edu
 "Turbos are nice but I'd rather be blown!"
    68 Camaro Convertible - 350 / TH350
       80 Toyota Celica - 20R / 5spd