ECM fault?

[Akselrud, Boris]

O2 output does seem slow when you scope it. We did replace it, but I am not
sure if it was genuine GM.
Also I would imagine that right after the replacement while the sensor was
brand new we should have felt at least some change in the idle character,
but there was no change.
That's why I am beginning to think that ECM program is causing it by
reacting slowly or over/under compensating the sensor input. Do you think
that it is possible? Of caurse if that's the case, I'll be stuck trying to
reprogram it.

Thanks very much for your opinion.

-----Original Message-----
From: Programmer [mailto:nwester at eidnet.org]
Sent: Monday, November 08, 1999 1:31 PM
To: gmecm at efi332.eng.ohio-state.edu
Subject: Re: ECM fault?


A slow rolling idle can be caused by an O2 that doesn't react fast anymore
or has become "poisoned". Have you replaced the O2 with a GM one ??--stay
away from the generic O2 sensors. Remember--in "closed" loop, the O2 sensor
is directly responsible for fuel control. The PCM just responds to what the
O2 sends--a biased lean O2 will also command a PCM "rich"--as well as a
biased rich O2 will command a lean condition overall.

Lyndon
-----Original Message-----
From: Akselrud, Boris <AkselruB at moodys.com>
To: gmecm at efi332.eng.ohio-state.edu <gmecm at efi332.eng.ohio-state.edu>
Date: November 8, 1999 10:11 AM
Subject: ECM fault?


>Unfortunately no one answered my first post regarding what I think is ECM
>related problem in 5.7 TBI in my 1993 Cadillac Fleetwood.
>The problem is erratic or I would say unstable idle. Looks like ECM is
>leaning the mixture (don't know for sure) causing idle to go below
>comfortable level for 2..3 seconds followed by 2..3 seconds of smooth
>operation.
>I've gone trough repeated sensors and parameters check on the engine during
>the last two years. I am confident that all the sensors working within spec
>and I scoped the output from all of them. Mechanical condition of the
engine
>is also good - no noices or knocks, compression tests like new, ignition
>system checked repeatedly and spark plugs replaced, no vaacum leaks.
Another
>words the mechanical condition is not at fault. However the output of O2
>sensor at idle is somewhat slow with a period of 2 seconds. I don't know if
>this is normal for that engine.
>Could anyone tell me if you have experienced similar behavior of the engine
>at idle and if you got it corrected. Can it be ECM induced?
>Please, share with me what you can, I have exausted all other sources.
>