[Gmecm] GMECM

[David Allen]

  Welding on the exhaust pipe with the O2 sensor conncted can work wonders
on an ECM and O2 sensor.  Seen this happen when the welder is grounded on
the car's frame and the exhaust isn't well grounded due to corroded
fasteners and rubber hangers. Wire welders have 18 to 30 volts on the
welding gun you can imagine what that does to a circuit designed for
millivolts! Ouch.
  When I have exhaust work done on my cars, I unplug the O2 before I hand
them the keys just to be safe.
  David


----- Original Message ----- 
From: "Rick McLeod" <dunvegan at sbcglobal.net>
To: <gmecm at diy-efi.org>
Sent: Thursday, November 03, 2005 6:19 AM
Subject: Re: [Gmecm] GMECM


> Most all late 80s to early 90s GM V8s ran a single O2
> sensor on the driver bank down pipe, doesn't matter
> what is downstream in the way of cross-overs, etc
> other than if the flow is increased so much that the
> sensor can't see enough heat to get warm, it won't go
> closed loop, which is a frequent problem in the likes
> of F-bodies that get headers added and low restriction
> exhausts (which I have and see it go open loop
> occasionally). In that case, replace it w/ a heated
> sensor to start with to rule that out, will probabally
> take care of the problem altogether.
> Also, get a data stream view of what the ECM is doing
> and see what is going on, is the O2 sensor working,
> BLM's close, etc, it may be as simple also as a broken
> wire to the O2 when the duals were installed, don't
> rule that out.
> Good luck
>
> > > I currently have a 1990 Chevy G20 Van. With a V8
> > 350 5.7l engine ECM
> > > 1227747
> > >
> > > its been running fine until i put dual exhaust on
> > it now its not
> > > running
> > > well at all the idle is very rough at idle and
> > also at slow speeds
> > > (most
> > > notably when its cold out)
> > >
> > > Ive been told by my mecanic i can be a number of
> > things but 02
> > > sensors seem
> > > to always come up as my ecu supports 1 o2 sensor
> > and with dual
> > > exhause i
> > > should technically have 2 ? Right or wrong?
> > >
> > > id like to possibly avoid doing a flash of the
> > eeprom as im not
> > > totaly
> > > familiar with it and was hoping that someone may
> > know of a solution
> > > to fix
> > > this problem . preferably not a real expensive one
> > ive invested
> > > quite alot
> > > of money in this truck and really want it running
> > well again
> > >
> > > thanks very much for your help -Mike
>
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