RE: IML: 82 Imp

-----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