Hi Volks,
    It would seem to me at high altitude where the air is less dense the afm
(air flow meter) flap will open less (lower wiper voltage to the ecu =
shorter injection pulses) for any given position of the throttle plate.  The
afm does a pretty good job of measuring the  amount of air / oxygen entering
the engine (if properly tuned).   As Bill points out the o2 sensor provides
the ecu with the all important  mixture info. Then with the o2 sensor
voltage the ecu further modifies the pulse length for a near perfect
mixture.  This all goes to hell in a hand basket if the engine, grounds,
exhaust, fuel injectors, tune-up item etc etc  are not in proper condition.
    The ecus in our beloved vans do not / cannot take into account we may
have a weak cylinder, an over or under active injector, bad plug / plug wire
to one cylinder, etc. It will adjust the mixture of all cylinders for a
proper o2 voltage from all cylinders. 3 cylinders can be running lean
because one is rich or miss firing.

Darrell Boehler
Makanda Illinois

----- Original Message -----
From: Bill <bill@FREEHOLDER.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Friday, October 29, 1999 12:10 PM
Subject: Re: Mileage at altitude

> Shouldne the O2 sensor keep the mixture right at altitude?
>
> At 09:04 AM 10/29/99 -0600, Richard A. Jones wrote:
> >I thought altitude compensation was handled by the fact that
> >the less-dense air moved the AFM vane less and so requested
> >less gas to be injected.  Not so?
>
> Bill (SE Arizona) (Bill@freeholder.com) HTTP://www.freeholder.com
> ----------------------------------------------------------
> It ain't what you don't know that hurts you,
> it's what you do know that's wrong.
>