ECM fault? Ignition ????

[Mike Rolica]

Now that I think about it sounds really plausible.  My great teacher once
told me that most problems are ignition related than fuel.

BTW:  Sorry for exhuming this thread.

I
Mike Rolica
EXT. 260
 :-)


	-----Original Message-----
	From:	Programmer [SMTP:nwester at eidnet.org]
	Sent:	Wednesday, November 10, 1999 8:53 PM
	To:	gmecm at efi332.eng.ohio-state.edu
	Subject:	Re: ECM fault? Ignition ????

	>>PS: Idle fluctuation is about 50..80 RPM, but when it falls it is
causing
	roughness and shaking the whole body<<

	Along Davids' suggestion about the pickup signal being lost --
that's
	EXTREMELY plausible--minimum signal RPM to the module must be at
least
	700mV. A weak magnet (reluctor) or cracked magnet is often the
cause. The
	centre brush of this HEI system must also be 3000 ohms--there can be
enough
	RFI to confuse the PCM into false triggering. Most aftermarket
brushes are
	lower in value. Another thing--if the MAP value follows RPM--the PCM
	commands rich as the RPM drops--and idle worsens. Even though the O2
may be
	cycling rich/lean at idle and you get a corresponding roughness--you
may be
	chasing the wrong thing. Ignition is critical to everything...

	My last word...about this thread

	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>
	Cc: 'n5xmt at bellsouth.net' <n5xmt at bellsouth.net>
	Date: November 10, 1999 11:27 AM
	Subject: RE: ECM fault?


	>1. I am dealing with the problem for three years
	>2. I've done all the
	
>scanning/scoping/replaising/maintanence/doublechecking/dealership/shop
	>3. I do have bought a service manual from Helm Inc and have it
memorized
	>4. I've done everything that was suggested so far by the mail list
and done
	>it multiple times in past
	>
	>I have stated in my original post that I have done all that you are
talking
	>about before I even though of posting on the mail list. What we
were doing
	>so far is reiterating things that have been done by me with the
engine.
	>
	>The objective of my post was to see if there is a commone
experience with
	>that particular engine and ECM which woudl cause such idle
behaviour.
	>Apparently there is not and I have an abnormal case.
	>
	>If there is nothing that I have not tried so far and nothing new
can be
	>suggested, then the thread is over.
	>
	>I am greatful for everybody's input.
	>
	>PS: Idle fluctuation is about 50..80 RPM, but when it falls it is
causing
	>roughness and shaking the whole body.
	>
	>-----Original Message-----
	>From: David Cooley [mailto:n5xmt at bellsouth.net]
	>Sent: Wednesday, November 10, 1999 11:50 AM
	>To: gmecm at efi332.eng.ohio-state.edu
	>Subject: RE: ECM fault?
	>
	>
	>Boris,
	>Blunt and to the point:
	>You said the vehicle has done this for 3 years.  Why suddenly it's
a
	>serious issue?
	>You haven't said how many RPM's the idle hunts up and down, you
haven't
	>provided *ANY* scan tool data IE: block learn/integrator (Fuel
learning)
	>values, recomendations have been made and you change the subject in
the
	>next message and skip over the suggestion.
	>Troubleshooting *MUST* be done in an orderly manner if it's to turn
up any
	>problems.
	>There is a wealth of info on this list and people that are willing
to bend
	>over backwards to help other list members out, but you have to be
willing
	>to take that advice and apply it or you'll get no where.
	>The first step you need to take is to buy a service manual so you
can check
	>the basics, Plugs, Wires, PCV valve etc.  the ECM/sensors should be
the
	>last thing checked after all the normal mechanical/vacuum related
items.
	>
	>
	>At 11:19 AM 11/10/1999 -0500, you wrote:
	>>I am wondering if there is anybody on that list who is doing
engine/ECM
	>work
	>>for living, has seen 5.7 TBI run smoothly at idle and has
experience with
	>>these, within drivable distance of New York City and don't mind
looking at
	>>my case?
	>>I feel I've done everything I could myself as well as
dealership/auto
	shop.
	>>
	>
	>===========================================================
	>David Cooley N5XMT Internet: N5XMT at bellsouth.net
	>Packet: N5XMT at KQ4LO.#INT.NC.USA.NA T.A.P.R. Member #7068
	>We are Borg... Prepare to be assimilated!
	>===========================================================
	>