RE ; MAC11 update

John Cody Forbes cody at
Wed Sep 10 10:07:36 PDT 2008

What Ben means to say is that all is well with primary ignition (signal 
output to the coil), but the ECU knows nothing about whats going on in the 
secondary ignition (everything between the coil and plugs inclusively) and 
won't store codes for these areas. Thats where the scope comes in. Get ahold 
of that scope, your problem will be diagnosed for sure.


Ben Swann wrote:
> Again - what do the MAC-11 codes say.  If 4 4 4 4 then all is well
> with ignition.
> Ben
> -----Original Message-----
> From: Rick Houck [mailto:rhouck at]
> Sent: Tuesday, September 09, 2008 10:38 PM
> To: Louis-Alain Richard; cody at; 'Ben Swann'
> Cc: quattro at; 'P Cole'; 'Ado Sigal'
> Subject: Re: RE ; MAC11 update
> 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
> [snip]
>> 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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