RE ; MAC11 update

[John Cody Forbes]

I think it's time to find that friend with the O-scope and you need to 
verify what is going in to the MAC11, what is comming out to the coil, and 
what is comming out of the coil. I've hit some confusing problems that are 
quickly and easily pinpointed by a scope.

-Cody


Rick Houck wrote:
> Louis-Alain,
>
> I have read through the suggestions on SJM's site, and feel that I
> have tested or eliminated things sufficiently, but since I have not
> yet found the problem, I am obviously missing something. Opening the
> ECU was one of the earliest things I did, since the problems started
> at a rainy track event. I found no evidence of moisture or water
> tracks, but dried it out in the sun just to be sure. After no
> improvement, I ordered a spare ECU and distributor from Force5.
>
> I have at least two of each of the major ignition and mechanical
> components, and I have tried about every combination of ECUs,plugs,
> wires, dist caps and rotors, complete distributors, coils, flywheel
> RPM and TDC sensors, knock sensors, fuel filters, and COMPLETE
> ENGINES. Nothing so far changes the situation except turning the
> distributor counter clockwise.
> It seems unlikely that I have two identically bad components, but
> maybe I do. It also seems unlikely that both engines have a sheered
> key on the cam or crank, but the relationship between the distributor
> rotor and the TDC trigger is good enough for starting but not for
> running at higher revs. The ECU is getting full voltage during the
> problems, and I also have confirmed ground (don't remember pin
> numbers now). As Ben says, ignition seems to be satisfied enough to
> start and run properly for the first 25% of the RPM range.
>
> Cody, I have some very loud exhaust backfires (3" from turbo back
> with no cat), but others come back into the intake system. I have
> been concerned that I may damage my turbo or intercooler plumbing.
> This indicates to me that the timing is getting confused at some RPM,
> or that the plug is firing at an improper time because of arching.
> When I changed plugs last week (again) the Bosch's had a dry carbon
> coating, but IMO nothing out of the ordinary for an engine running at
> low speeds. New plugs are NGK's, but results are the same.
>
> Rick
> about to give up
>
> ----- Original Message -----
> From: "Louis-Alain Richard" <laraa at sympatico.ca>
> To: "'Rick Houck'" <rhouck at neo.rr.com>; <cody at 5000tq.com>; "'Ben
> Swann'" <benswann at verizon.net>
> Cc: <quattro at audifans.com>; "'P Cole'" <pcolegrps at comcast.net>; "'Ado
> Sigal'" <a.sigal at bluewin.ch>
> Sent: Monday, September 08, 2008 11:11 PM
> Subject: RE ; MAC11 update
>
>
> 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.
>
> Louis-Alain
>
>
>> -----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