3 computers

[DMC3165]

Hi all. I was curious about the 3 computers in the lambda compartment. Which one is which and what are their functions. My car is bone stock and all 3 are hooked up.

Thanks,

[Bitsyncmaster]

Lambda ECU, Idle speed ECU and Ignition ECU.

note: None have a CPU in them.

[DMC3165]

Lambda ECU, Idle speed ECU and Ignition ECU.

note: None have a CPU in them.

Ok which one is which.

[Chris4099]

First off, just for clarification, this car's version of a "computer" is not what you would typically consider a computer today. They are mostly analog devices. They don't run microprocessors with programming. They simply take different inputs and drive different devices accordingly.

First off is the Lambda system. It's in the bottom right and is vertical (connector is on top). This takes the measurement from the O2 sensor as well as a temp sensor and will then adjust the PWM ratio of the frequency value. This has the effect of adjusting the fuel mixture. So when the car is running lean, it will try to make it richer and vice-versa. By keeping it at the proper AFR, the emissions are as clean as possible. Pic:
http://store.delorean.com/p-10479-ecu-lambda-black.aspx

Next is the idle controller. This is on the top left and has two plugs on it. This takes the RPM info and adjusts the idle speed motor accordingly. Without it, the air flow into the engine would be fixed at idle. Since different conditions can cause it to otherwise fluctuate, it keeps the idle stable at 750. This is regardless of engine temp, air temp and engine load (such as having the AC on). Pic:
http://store.delorean.com/p-6720-idle-speed-ecu.aspx

Finally there's the ignition module. In the distributor is an induction coil and trigger wheel. By measuring the pulses, it can tell when it needs to fire the ignition coil. Basically it's used to replace and emulate the older style points system. This generates the RPM signal that's also used by the RPM relay and tach. Pic:
http://store.delorean.com/p-6851-ignition-module-ecu.aspx

[Rich]

And the good news is that all 3 of them together cost a lot less than one Body Control Module, a real computer, for any modern Ford you care to name.

And they do a lot less, as noted....

The other good news is that they are fairly reliable and when they aren't, well, we can still get replacements 32 years after the cars were made.

[jawn101]

Or Dave M can replace all three with an IC the size of a shirt button. "Whatta ya mean, Doc? All the best stuff is made in Japan" :)