ECM fault?

[Akselrud, Boris]

I is certanly not several times a secont at idle. It is more like Once every
two seconds. When you increase RPM to 2000 it becomes faster.
I always wish I had seen another engine like mine and scoped the O2 output
on it, but haven't done so so far.
I haven't tried to measure )3 output with disconnected harness. I will do
so.
The engine always acted like that as far as I can remember.


-----Original Message-----
From: David Cooley [mailto:n5xmt at bellsouth.net]
Sent: Tuesday, November 09, 1999 10:00 AM
To: gmecm at efi332.eng.ohio-state.edu
Subject: RE: ECM fault?


At 09:37 AM 11/9/1999 -0500, you wrote:
>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.

The way O2 sensors work is they swing rapidly from rich to lean... Should 
be several times a second.  If it's slow, then maybe there is a problem in 
the harness with a bad connection.  Try looking at it's output with the O2 
sensor disconnected from the harness...  Will set a code, but should see 
the voltage swinging properly until the ECM commands full rich mode to 
protect itself.
Was anything done to the vehicle before it started acting this way?

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