mac 10 ECU question

[Todd Phenneger]

Just to confirm,
  Did you replace the temp sensor at the BACK of the head of the
Front.  If you  replace the wrong sensor then it wont do
anything.  To me that still sounds suspect.  Have you checked
the current coming from you DPR yet. You mentioned you got a
Fuel Pressure Tester and tested the DPR, was that by simply
watching the change in fuel pressure as the car warmed up?  If
thats all you did I'd still tune it to match the specs in the
bently. Its the grey box on the side of the Dist.  HTere is a
test procedure for checking the current.  "or is it voltage, I
THINK its current as it has to be checked in line.  But anyhow,
find the check section for this and check it out.
  Good Luck
    Todd

--- 4wheeldrift <4wheeldrift at driftunderground.com> wrote:
> 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.
>


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