MAC11 update

Rick Houck rhouck at
Mon Sep 8 19:38:49 PDT 2008


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.

----- 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

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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