RE ; MAC11 update

Louis-Alain Richard laraa at
Mon Sep 8 20:11:05 PDT 2008

Well Rick, I have no answer to your turbo question, but before looking for a
mechanical failure, which is always possible but usually shows some
evidence, please complete the ignition route first.

If I remember well, you never mentioned any diagnostic at the MAC-11 ECU
itself, just that there was no codes ? I would open the ECU to see if
there's any water or corrosion in there. If not, I am sure there is a way to
test the boost pressure transducer in situ without an oscilloscope but with
a mighty-vac and an adjustable timing light, or something like that.

I once had to find a running problem on a friend's urQuattro, and an ECU
swap was the solution. But we arrived there after completing the whole
official diagnostic procedure, which is long and fastidious, and the ECU
replacement was the very last step.


> -----Message d'origine-----
> Guys,
> I think things are pointing to a wiring problem, but have a couple of
> questions first: Could a turbo that doesn't spin as easily as when it was
> new cause backfires?  My Garret GT2871 ball bearing turbo still spins up
> (as
> I can see when the cone filter is off), and I can hear it coast down after
> shutdown, but it is not quite as smooth as when it was new 3 years ago. I
> have not checked end play, but it certainly is not enough to cause any
> contact with the housing. I can't get enough RPM to get the boost up much,
> but it does get started up the dial before the backfires start.
> I don't have an o-scope, but I think it is time to find someone who does.
> Rick

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