Re: Does the ECU learn & adapt?

["Scott Mo." <scottmo@teleport.com>]

Rob,

> My most recent experience was replacing the oxygen sensor. After
> replacement, the car ran better. But for the next, say, 100 miles I >was getting _terrible_ gas mileage. Now, the mileage seems to be >improved over before I changed the OXS, which is what I expected. I >feel like others have suggested that the computer adapts to how you use >the throttle and such.
> 
> So, what's the scoop here? Does it learn? Is there a way to "reset" the ECU?

Yes, the Motronic system in the 1991 200TQ 20V does have an adaptive
capability to adjust the mixture over time by monitoring the O2 sensor
operation, Here is what the service training info says regarding this:

"A system is said to be adaptive when it is capable of replacing
standard control values with modified values due to changes in operating
conditions. Adaptation by way of example of the lambda (oxygen) control
system.

For example: When the oxygen sensor senses that the fuel mixture is too
rich, the control unit changes the fuel mixture to a leaner value by
shortening the injector opening time. If the mixture is still too rich
and the control unit's rich limit is exceeded, the control unit will
adapt to this condition and establish a new basic setting. This new
basic setting (pilot value) will then be used in both open and closed
loop engine operation. This eliminates the need for periodic CO
adjustments." End quote.

Note: The Carbon Monoxide (CO) adjustment referred to is the idle
mixture adjustment.

If you remove fuse #27 with the engine off, this will remove power from
the ECU and should erase any adaptive memory stored as well as any
stored fault codes.

HTH
-- 
Scott Mo.
1989 200TQ
http://www.teleport.com/~scottmo