Disappointing MAC11 update

Rick Houck rhouck at neo.rr.com
Wed Sep 3 18:57:34 PDT 2008

MAC11 updateAnother update: no change. 

My bright idea today was that my engine monitor system (Innovate Motorsport #LM-1 with RPM and aux inputs adaptor) was triggered by the MAC11, and that might be causing some problems, but that proved to be wrong. The RPM signal to the monitor comes from the fuel 034EFI ECU, not the ignition ECU, so disconnecting it did not have any effect on the backfiring.

Ben, unfortunately I scrapped out the MC flywheel long ago as never to be needed, but the 7A flywheel has only one pin on the engine side (I have a spare for comparison), with no other holes for pins There are two on the tranny side, but I understand that these were needed only by the factory for something. No pickup for those anyway.

I have verified continuity from the two flywheel sensor plugs to the ECU connector to identify the proper connection, but did not ohm check the sensors themselves (but I have used two different sets with same results). I forgot to check clearance from sensors to the flywheel teeth and single pin before reassembly.

The coil seems to be a valid suspect, but I am on my THIRD one! I am now out of Audi coils, and will have to try something else.

Questions to you fellow do-it-yourselfers:  
1. Can I use any standard can coil for a test. I have one from an old Porsche project that is still good. Any BTDT?
2. can anyone confirm that the TDC pins are in fact in the same place on both MC and 7A flywheels, just to reassure me that the bad fairys didn't move it and fill the hole?
3. a rough measurement of the depth from the sensor mounting surface to the pin looks like more than what is called out in Bentley (0.060"?), but it is hard to get a good depth reading down there for comparison to the sensor. Guess I should verify this, right? Yea, I know...........

Thanks again for the help. What a great place to bounce ideas.

  ----- Original Message ----- 
  From: Ben Swann 
  To: rhouck at neo.rr.com 
  Cc: 'Ben Swann' 
  Sent: Wednesday, September 03, 2008 9:45 AM
  Subject: MAC11 update


  With exception to the possibility of the pin on your flywheel being different than the stock MC-1 flywheel, everything else is straight-forward.  You basically set the timing up statically as per timing-belt installation followed by setting the distributor dead "in-window".  That means with flywheel at TDC/0 mark hash lined up with bell-housing pointer - that should correspond to #1 piston being at its topmost of travel (meaure carefully with rod) and if it has not slipped, the front pully should line up with TB cover dimple or oil pump pointer - although I would not use this as a primary reference since these do invariably slip.  

  Then the cam sprocket should be aligned with rear hash mark at the cam cover gasket and watr pump locked down to tighen belt.  Then the distributor is rotated so middle of rotor is pointing to the hash mark on edge of distributor.  The number 1 plug wire will be at the hash mark.  Set it and forget it.  No timing light is used - maybe to see if getting a spark, but I usually just ground the number one plug for that test.  If spark - then ignition is working - move on to diagnosing fuel issue.

  The above does not rule out bad wires, cap, rotor or coil, but lets you know that the timing is set correctly.  There is no adjustment of timing that can be done short of a remapped chip.  Timing may retard for various reasons during operation - IAT high, knock detectoed or other sensor input, but usually not enough to even be noticable - certainly not what you describe.  Usually if there issignificant  retard, a code will be set and should be pulled prior to engine shutdown as MAC-11 is volatile whereas MAC-14 and 3B retain codes until they are cleared.

  As far as I recall, although the 7A flywwheel is a different thickness, etc. the pins are in the same place with repsect to TDC as the MC and 3B flywheels.  The 7A uses the same timing synchronization method as the MC-1, MC-2, and 3B engine control units and the glywheel sensors need to be present and providing a good signal.  You may want to verify they are the same - I may have one to compare as I'm in middle of a swap and pulled my 7A.

  Any problems with distributor out of alignment or signaling problem with hall or flywheel sensors will generate a code.  4444 means that everything is checking out good - except that you may have the wires in the wrong places in the cap - no start or backfiring.

  See ****comments below after your questions. 


  [Date: Tue, 2 Sep 2008 22:39:27 -0400 
  From: "Rick Houck" <rhouck at neo.rr.com> 
  Subject: MAC11 update 
  To: <cody at 5000tq.com> 
  Cc: quattro at audifans.com 
  Message-ID: <001901c90d6e$48c65190$6401a8c0 at rick> 
  Content-Type: text/plain; format=flowed; charset="iso-8859-1"; 

  Thanks to Cody and everyone who offered ideas. I went back in the garage tonight and confirmed a few last details. Here is what I did (some for the umpteenth time):

  1. installed brand new plugs-no change 
  2. installed used distributor cap and plug wires from another motor-no change 3. changed entire distributor with good used one and new rotor- no change 4. checked firing order and correct rotor rotation, then flywheel, pulley, rotor marks and #1 plug wire to make sure - all correct and lined up 5. re-indexed plug wires off one position in either direction - no start 6. checked for codes - all well (4444) 7. attached timing light and looked for mark on pulley and flywheel - NO SHOW!!

  8. Reved motor while watching other visible marks on flywheel and pulley - they advanced gradually until I got around 2400 RPM then the light quit firing everytime as the engine missed and backfired.

  *** Sounds like you had it to the point where you can declare ignition good.  Again, if the engine starts and runs, then ignition is OK.  Nothing else to do.  Move on to fuel or compression issues.

  9. rotated distributor after it was running to verify that it ran better and reved almost like normal - same as before, it did, but would not re-start if left in that position 10. unplugged knock sensor to see what would happen - no change 11. swapped RPM and crank position sensor connections - no start 

  *** I got these mixed up once and drove me crazy.  To verify you have the sensor wiring correct, it is a good ide to use a VOM and do round-robin continuity check on both flywheel sensor wires, and  knock sensor as they all use the same colored wires.  Basically you measure continuity ( 1K?) while sensor connected at firewall, then confirm correct sensor by disconnecting it - then mark as per proper color code.  I received a wire harness that had the color code bass-ackwards for the knock sensor and one of the flywheel sensors.

  12. pulled starter to verify that no teeth are damaged or missing and that the flywheel pin was still there - teeth showed only minor signs of stupid engagement while engine running sometime in the past and the pin was there, and no other holes (with a missing pin) were found 13. Decided to give up and drink a full keg to drown my misery, but didn't have one.

  My conclusion: 
  I think all the individual parts are working properly but the timing pin is in the wrong location. All of my last 9 years of track events with this MC1engine and 7A flywheel performing beautifully are just a figment of my imagination, or a bad fairy came and modified my flywheel between run groups. I'm at a loss to understand it now, unless something has been retarding my timing just enough to offset the incorrect position until recently.

  Shouldn't I be able to see the TDC "0" mark on the flywheel with the timing light at idle (I think so), or on the front pulley?

  *** Not really - timing belt just does not work for this type of ignition setup - all you see is a flashing light. 

  Is there any way I could have installed the 7A flywheel off one hole? - I don't think so, but I just went until all the holes lined up for the bolts without trying the next position.

  *** No holes are drilled to be idiot proof. 

  How do I find the correct position for the pin, so I can hopefully redrill and install it through the starter opening? 

  *** unless pin sheared off, the pins (2 of them) should be there or you will not location of pin where there is a sheared off pin. You'll need to drill it out and install a new pin.  I know - easier said than done.

  Can I simply pull the pin sensor while the visible mark is on the "0" and mark that location, or is there an offset of a few degrees?

  *** Pins are not at TDC on the flywheel, but are more like 60 degrees and offset by 20 degrees - no these are not exact.

  Thanks again to everyone. 

  frustrated Rick] 

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