Date:         Thu, 31 Jul 2008 22:16:14 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: ECU and lean idle
Comments: To: Mike Elliott <camping.elliott@GMAIL.COM>
In-Reply-To:  <48924AC8.4050801@gmail.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 04:29 PM 7/31/2008 -0700, Mike Elliott wrote:
>it helped? Don't recall). Second, the O2 gauge on the dash doesn't show
>any lean condition.
>
>So maybe the loaner ECU was also whack in the same way, and maybe the
>dash O2 meter is not seeing what their sniffer saw for some reason?

I suspect their sniffer was looking at excess hydrocarbon...if you
have a problem with one cylinder not firing well, the lambda sensor
will see the oxygen being passed through from that cylinder and lean
the heck out of the mixture, trying to make the oxygen go
away.  Ditto any exhaust leaks, they suck as well as blow so false
oxygen gets to the sensor.

Your ECU might benefit from cleaning the coating off the back of the
board and resoldering the joints.  I'm sorry to say that the four
ECUs I've looked at from that period, both Bosch and Adler, *all* had
significant trouble with solder fatigue -- and  the Bosch ones for
sure (can't remember the Adler) part of the trouble was that some of
the component leads were dirty and had never been properly wetted by
the solder.  One particular offender was a big fat resistor near one
edge of the board that was involved IIRC in the AFM circuit.  Also
the FI drivers, and I seem to remember some big diodes as
well.  Anything with either a lot of thermal cycling or a lot of mass
hung off the board or both is very prone to this, as solder has
virtually no fatigue resistance at all.   This stuff is hard to see
without a 30x microscope, unfortunately.  I can probably dig up a few
pictures if there's interest.  But a slow, patient job of sucking the
solder off a joint, cleaning the lead until it tins nicely and then
resoldering the joint and go to the next one -- while a royal PITA --
will take care of the bad joints whether you can see them or not.

david


--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"