MAC11 update

John Cody Forbes cody at
Mon Sep 8 20:52:31 PDT 2008

What do the spark plugs look like (rich, lean, etc.)? Is it backfiring out 
the intake or exhaust?

The turbo isn't your problem. I driven a car with a turbo that has blown to 
smithereens and the only performance loss was the lack of boost and the 
exhaust leak because of the hole in the exhaust housing of the turbo from 
where the turbine wheel came through it.


Rick Houck wrote:
> Guys,
> Again, thanks for your input. Had to step away for a few days before
> my frustration level overflowed.
> Tonight I removed the factory coil from my ES2 coupe and put it into
> the 10vt coupe and there was exactly zero change. That was the fourth
> coil so I can be certain that it is not the cause. Someone suggested
> a fuel filter change, and although my fuel pressure has been where I
> expected, I changed it with no effect on the problem. I raised and
> lowered the static pressure with the motor running and the problems
> persisted.
> I went into my 034 stage1a fuel ECU and re-loaded the base map that I
> have run successfully for a couple of years. When that did not change
> the backfiring, I tried 3-4 other maps with no success. BTW, my cam
> sprocket has 5 pins and a Hall sensor to run the fuel only, and all
> the pins are there and not bent.
> 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
> ----- Original Message -----
> From: <cody at>
> To: "Louis-Alain Richard" <laraa at>
> Cc: "'Rick Houck'" <rhouck at>; <quattro at>
> Sent: Wednesday, September 03, 2008 8:02 AM
> Subject: Re: RE : MAC11 update
> I'm with Louis-Alain, I think the coil is the next place to look.
> Think of it this way - if the flywheel was damaged it's not like the
> damage would dissapear at low RPM so why would it run correctly then?
> If the pin was off the timing would NEVER be right, unless the pin is
> switching it's position in the flywheel in real time ;-).
> Here's another data point - the tach is run off the ECU. If there is a
> problem in the ignition related inputs (flywheel sensors) the tach
> would go haywire or stop working all together. If the tach seems like
> it's indicating correctly then the issue is an output problem, not an
> input problem. It's entirely possible that the igition coil is failing
> and just can't produce a big enough bang when the frequency demand
> increases. Rick, whats the chances of you (or a buddy) having an
> occiloscope?
> Oh and I like this "... gotta love the supportive way folks operate on
> the "quattro list" these
> days ... " by Steve B. Not only does he write that about Huw's post,
> but he completely neglected to read Ricks post and asked Rick to test
> exactly what he spent time detailing out about what he did last night.
> Good stuff.
> -Cody Forbes
> Quoting Louis-Alain Richard <laraa at>:
>> How about the coil, Rick ? Could it be at fault when the RPM rises ?
>> Louis-Alain 

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