-----Original
Message-----
From: Ken W Stephenson [mailto:kss37215@xxxxxxxx]
Sent: Wednesday, May 11, 2005 7:11 PM
To: dickb@xxxxxxxxx
Subject: 82
Imp
To paraphrase Columbo,
there's just one more thing, Dick. The reason
I
got on the computer kick was
in one of the few times I got this thing up
to running temperature, I
tried the trick of biasing the oxygen
sensor
lead by touching the battery
posts with my left hand while holding the
terminal. There was no
change in the idle. Does this indicate the
CCC
is still in open loop?
Sounds like it. Have you checked the
resistance of the EFI coolant temp sensor? They do fail, it's rare
but I've seen a bad one. If it fails shorted, the CCC stays in the
cold engine mode. If it fails open, (which is much more likely),
the CCC goes to the hot engine mode, so you can check by unplugging the
connector when the engine is cold and when it is warmed up – it should
make little difference when the engine is warm. You can also check
the resistance between the two prongs – it should be somewhere around
900 ohms at room temp, and much higher (1500 ohms or so) at 180F.
Don’t remove the sensor unless you are certain it is bad AND you
have a replacement handy, they often crumble when you try to take them
out! This is the two prong sensor mounted at the top front of the
engine at the upper radiator hose connection, not the switch type
mounted under the AC compressor. Be gentle with this critter, it
is brittle and it is very hard to find a
replacement.
Another thought is that it takes a Looooong time
to get everything into normal operation, especially if you have been
disconnecting the battery each time you park it. The memory gets
wiped, and it has to go through the whole "calibration" routine each
time you do that.
I assume you are familiar with the calibration
routine – if not study this in your FSM. If you just put the car
in normal service, it will calibrate itself, but you need to drive it
for a while to do this. Otherwise, you can do it in your driveway
by following the procedure given in the FSM.
And, there's just one more thing (right back at
you, Detective): The keep alive wire to the memory is the most
vulnerable wire in the harness - it's the lonesome red #18 wire that
dangles out from the 3 wire connector under the CCC. If this becomes
damaged (and it is easy to stress this guy when you remove the air
cleaner assembly to work on those nozzles!), the CCC loses it’s memory
ability, so the car becomes like the Alzheimer’s patient who can hide
his own Easter Eggs – every day is a new day! (This is the same as
disconnecting the battery every time you turn off the
engine).
To further explain this, I'm going to strip
in here a quote from Bob Harris, a sometimes IML member who knows more
about these cars than anyone else around, I
believe:
For a cold EFI car,
provision has been made for the "warm-up"
transition
phase - it is the CCC Memory
Module. Therein lies a fixed program
that
provides Idle Speed and
Fuel/Air Mix Ratio and Ignition Timing to
maintain
the engine until it can be
more efficiently controlled by the output of
the
Oxygen Sensor. Also, during
this time, no vacuum is allowed to either
purge
the Vapor Canister nor have
fresh air blown into the rear-most Cat
Converter; the EGR valve,
also with a temp sensor, will not operate.
You
will notice a beautifully
smooth drop in "Fast Idle Speed" as the
engine
warms. The Coolant Temp
Sensor will warm-up and send a signal to
the
computer which will send a
signal to the 70 second Timer which will
proceed
to "Time Out." After that
time, the Air/Fuel control, via the CCC,
is
handed over to the Oxygen
Sensor and we have Closed Loop
Operation. Then the
"Bracketing" may begin, the
Vapor Canister purging begins, the
Diverter
Valve now sends air to the
rear Cat Converter instead of the back of
the
engine heads, and the EGR
Valve begins to operate, the Air Flow Sensor
comes
to life and contributes to
the plan and ignition timing becomes a
function
of what is necessary for
optimum operation. We now have ideal conditions
of
Fuel Management and emission
requirements.
My comment on the above: I think Bob may
have made a small error: It seems that the air flow sensor comes
into operation as soon as the key is released from the “start” position
– that is why the car will start by stall with the lid off the air
cleaner, even when it is ice cold.
I got so many pleas to keep this discussion on
the main IML that I’ll go ahead and post it to the list – when people
complain maybe we’ll have to start a sub group for these
cars.
Dick Benjamin
