ECM Fault?

[Akselrud, Boris]

MAP sensor is fluctuating constantly along with the idle - I think that's
normal i.e. with RPM change you get pressure change. I did scope just about
every signal, including the MAP. The map signal is not flat, it has waves
corresponding each cylinder I guess, one of them is specially large. I think
It is because it is close to that particular cylinder. Wave amplitude is
approx 0.1 to 0.2 V on the largest wave.

I am desparately trying to complete the device to inject the fuel to
disconnect ECM and see if idle is still fluctuating. If it is, it would
indicate the mechanical problem.

-----Original Message-----
From: David Cooley [mailto:n5xmt at bellsouth.net]
Sent: Monday, December 06, 1999 4:17 PM
To: gmecm at efi332.eng.ohio-state.edu
Subject: Re: ECM Fault?


Good point...
What does a vacuum guage show on the engine?
Steady or fluctuating?  Could be a burnt valve, flat lobe on the cam etc 
making the MAP vary.  Scope the MAP output and see what it looks like.


At 01:02 PM 12/6/1999 -0800, you wrote:
>"Akselrud, Boris" wrote:
> >
> > What I found by
> > looking at the signal with an oscilloscope is that there is an
additional
> > abnormal impulse approximately 0.1 .. 0.3 ms wide in between the normal
> > impulses opening the injector. This abnormal impulse comes and goes,
> > perfectly corresponding to idle rpm fluctuation. Even when I step at the
> > accelerator pedal, up to a 2500 rpm I can see the abnormal pulses and 
> again,
> > they are not always there, they come and go with 1..2 sec interval.
>
>These pulses are the result of "acceleration enrichment".  Your ECM is
>sensing the TPS opening, and/or the MAP pressure increasing, and/or it
>is opening the IAC.  All three events will cause extra fuel to be
>injected asyncronously of the normal injection.
>
>The question here is - is the AE the cause of your unsteady idle, or is
>the unsteady idle causing the AE?
>
>--
>Ludis Langens                               ludis (at) cruzers (dot) com
>Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/

===========================================================
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!
===========================================================