Just a small piece of info from an old tech.
The "chip" is the starting place for the computer or ECU to begin.
It holds the original set of parameters for the car to operate from, such as enrichment, dwell, timing, etc.
After you have run the car for a while, the program changes slighly to allow for filters not passing as much air, or exhaust systems plugging up (cat converters) , plugs wearing out and other "replaceable" items.
Each time you service the car, you should reset the ECU.
This is very easily done by disconnecting the battery for a short time to allow the "learned" memory to drain and make the ECU run back to the "chip" to get the original parameters for running.
I usually disconnect the battery as I service, or disconnect and go for coffee.
The factory says the reset happens in a few seconds, but I have seen capacitors hold a charge for several minutes, hence the time I allow for discharge.
Hope this helps.
Bob

Good point Bob, they are indeed "adaptive"!

JimT: funny.......... as,......... #$%^&.

My bad, regardless.

My best (always),

True for 964's, but not for Carrera's. There is no adaptive functionality with the 3.2 Motronic.

ianc

Thanks ianc! I knew I had read that about the 3.2s, and here is a post I found:

The reason I thought that the DME ECM could suddenly lose its mind was based on what I read in Bentley on pg 240-4. The note there says that poor driveability could result if the battery had been disconnected previously (mine wasn't) because the DME adaptive memory is erased and that after 10 min of driving it re-adapts. So now I'm confused. Is Bentley wrong?


Someone else replied that the Bentley manual is indeed wrong in this regard. Sorry about passing along bad info...live & learn :).