mac 10 ECU question

[4wheeldrift]

It ran great then just started to run poorly one evening. I bought a
brand new fuel distributor and DPR and I have swapped them around
without improvement. I thought it was the temp sender but I replaced it
with no change. I also replaced the O2 which had failed with the correct
Bosch heated unit. Then my Bentley Manual arrived and I tested the
altitude sensor, air plate sensor, I bought a fuel pressure tester and
tested the pump and DPR. I really think it is the ECU. I have an
air/fuel meter and I don't see it hunting for a good mixture. As a
matter of fact the car seems to run just as well except for idle speed
with the ECU disconnected. The control unit is the only piece of the
puzzle I am lot able to locate a replacement for. Well within my budget
anyway. I didn't realize that the mac10 had an open loop / closed loop
running scheme. It makes me want the conversion over that much sooner.
My only real hitch in not doing the swap right now is my Saturn just
lost its transmission's OD and I am still having the engine rebuilt in
my corvette.

John

-----Original Message-----
From: quattro-admin at audifans.com [mailto:quattro-admin at audifans.com] On
Behalf Of urq
Sent: Friday, October 03, 2003 12:35 AM
To: quattro at audifans.com
Subject: Re: mac 10 ECU question

Frankly, I doubt it would be wirth the effort.  I suspect that the OXS
feedback system will not work ... and that is all you're getting if you
don't hook up the ignition stuff.  I'm not a complete expert on the
internal
code, but from what I have seen I suspect the code won't really loop
unless
it is getting the proper gating signal from the Hall Sender in the dizzy
and
the engine timing sensors on the flywheel (at least the reference
sensor).
Since you would need to be switching from the DPR to the CPR/OXS Freq
valve
for mixture control, it sure seems to me that you would need to swap in
the
MC's fuel distributor ... and who knows what that would do when hitched
up
to an NA car ... I don't know what has transpired in the past on this,
but a
mixture problem sounds like a differential pressure regulator or control
module issue to me ... and it is always worthwhile to test system and
control pressure ...

Steve Buchholz
San Jose, CA (USA)
> --
> I have been having problems with my 85 4k Quattro for about a year
with it
> running way rich at idle and too lean at cruise. I have tried
everything
> except swapping the ecu. I have a complete mc motor with the harness
and
> ecu. I am looking at swapping the mc fuel management system (mac 10
ecu,
> fuel distributor, injectors and harness) over to the stock motor until
I
put
> the turbo motor in. My question is which sensors besides O2, full
throttle
> switch and Idle switch are required if I only need the fuel side of
the
ecu
> and will it work with the rpm and hall sensors not connected.