Set meter to duty cycle and insert the red probe in the #3 hole in
the circular test plug with the screw cap on the fender. Black probe
goes into #2, or ground, or in the case of my cheapo meter, no
contact (doesn't read anything with it connected for some reason).
The resultant reading is the relative "on" time of the square wave
generated by the computer.
It should read 50% with the key on, engine off, 50% until the O2
sensor warms up, and then float around 50% as the computer controls
the mixture.
Some read 20% ignition on engine off, so don't think you have a bad
computer right off. If it reads 0 or 100%, you have a computer
problem (no signal), and if it starts out at around 50% and then goes
off scale either direction, you have a fuel delivery or air leak
problem.
The mixture is adjusted via a recessed 3mm or 4 mm (I don't
remember) hex socked nut accessable through the small tower that
goes up the the top of the air filter housing -- if you have a long
allen wrench, you can set the mixture with the air filter in place.
Press down gently to engage the socket into the actual adjustment
screw, turn a bit, lift the wrench up. You always press the lever
down some while adjusting, which will make it go rich. Wait at least
20 seconds after adjustments to stabilize the sensor reading, or
believe me, you will be chasing the mixture all over the place!
Fix all the vac leaks first -- you can use brake parts cleaner spray
to find them. Likely you will see the split idle control valve hose
when you pull the air filter housing!
Peter
On Dec 7, 2008, at 6:57 PM, E M wrote:
erm, I think you can test the O2 sensor using a multimeter set on
dwell from
the test spot on the front left (driver side) fender.
I forget the exact procedure, but someone here knows, is it Peter?
Ed
300E
2008/12/7 Mitch Haley <[EMAIL PROTECTED]>
Hendrik & Fay wrote:
It is a matter on focusing on the things that change from when an
engine
is cold to when it is warm.
I'd like to know if the lousy running coincides with the
changeover from
open loop to closed loop. If so, I'd be interested in certain
sensors that
are ignored in open loop, like the O2 sensor(s).
Mitch.
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