ECM fault?

[Mike Rolica]

Umm just a simple though for a simple check... take the drive belt off and
see if it does it then :-)  reason:  on my 2.8 v6.. alternator kept pulling
down rpm cause ver and bearings were bad, same sort of thing  ECM supposed
to compensate for it but was too much load causing it also to be rich.
Later I had the same problem with the air pump.. one of divert valves was
bad.. would build up pressure the blow off relief causing idle to go up...
down.... Up.... Down...
Don't always point to ECM.... Problem is these days too many people
including most shops depend on their scanner too much.. Weakest and most
unreliable part of a motor is the mech. parts... not the electrical  Check
things that wear, or move first,  even if it has been replaced,  don't
automatically rule things out just because you replaced them too.  Keep
going over this, starting over 2, 3 5, maybe 10 times, until you are 200%
sure check recheck,  rarity is for ecm's, electrical parts to go bad under
normal use.
Mike Rolica
EXT. 260
 :-)


	-----Original Message-----
	From:	Akselrud, Boris [SMTP:AkselruB at moodys.com]
	Sent:	Tuesday, November 09, 1999 9:38 AM
	To:	'gmecm at efi332.eng.ohio-state.edu'
	Cc:	'nwester at eidnet.org'
	Subject:	RE: ECM fault?

	I just verified that Oxygen sensor we put was genuine GM. The
output,
	however seems slow. Maybe it should be, because the mixture might be
	leaning/riching slowly.

	-----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.
	>