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Hi my name is Adam Prince and I work at Crisp Line Metal Forming.
Normally we specialize in doing classic cars, but today
one of our own vehicles is having some problems.
I pulled up a code on it and it came up as an air fuel metering problem.
My knowledge isn't in depth on modern car's
electronics but I am capable of learning.
One of the best books I think there is
is Automotive technology by James Haldeman.
I'm not associated with him but I've used a lot of his information
successfully.
To test the oxygen sensor
it is a
four wire
oxygen sensor.
you can see here there is four of them
and two of them are for the heater
and two of them are signal wires.
Now I don't have a wiring diagram so
what I did is put one lead
to the ground
and then other lead I poked around in here
until
I start getting a variable reading between
somewhere between 100 mV to about 800 mV.
and what I'm going to do is run a test
and this being a 1999 Ford Escort
it is the white wire with
the green strip
The white wire with the green strip. Were just plugged into the back
through probably silicone (the cap on the plug comes off to expose silicone).
I'm going to start it up now
(Engine noise) Nice thing about James Halderman
is that he gives very clear instructions in his book.
So were going to turn it up to voltage.
Let the meter go on.
It's on, get it to DC.
There we go, see it's fluctuating everywhere. I cannot tell what the reading is.
So what we do is, according to James Halderman, is hit the Min/Max button.
And the engine has already been warmed up previously. I took it for a drive.
So were going to let it read for a couple of minutes.
And according to the book
We should have a maximum reading
above 800 mV
So let's check this out.
Point 866 volts.
Ok, that looks to be within spec.
And then we hit the button.
We get a Min of
167 Mv.
The book says the minimum reading should be
less then 200 mV.
So everything looks OK with the oxygen sensor.
They additionally recommend
that you hit the average button.
We don't have an average button and so we cannot really investigate that. But what we can do...
is purposefully
induce a lean condition in the engine.
One way we can do that is purposefully causing a vacuum leak.
Previously I pulled this off here
to the brake line booster.
What should happen is
is this should go down.
Indicating a very lean condition.
I've already done it so I'm not going to do it.
Then to induce a
rich condition (Hits max button)
What we can do is take the carb cleaner
Open up air filter really well
and squirt it in there (Past the Mass Airflow Sensor, the black bump near the air filter above the ohm meter with all the wires going to it).
And then it should shoot up the max.
So this is testing out right now so i'm thinking that we don't have any problems
with the oxygen sensor.
So we will continue our investigation.