Misfire Module B

The Mechanic Said:

...  that during warm-up, which is closer to idle, that the exhaust was running pretty black and rich.  After warm-up, and at higher RPMs, even during ignition checks, the exhaust looked good. 

I want to throw my give into the ring with the Choke/Enricher Circuits which only works to produce a Rich/Sooty mixture when near idle.

In looking at your opening post, it could also be interpreted as instead of One lean looking cylinder and three normal ones, you could also interpret that what you have is 3 Overly-Rich cylinders and one good one.

I have no clue as to why they wouldn't all be the same. ???

Thomas Odehnal wrote:

By the way, from my buddy's experience as an auto mechanic, and doing the simple listen and watch analysis, he would be leaning towards an electrical issue , rather than carburation.  ......Tom 

Did he suggest you try spark testers?

When you say, "The right EGT was running about 200 degrees hotter",  Do you mean the temp went UP when it started missing?

Do you have 4 EGTs or only 2?

Which cylinder was the one that changed?

Hi Bill,  I bought a spark tester and I could not identify a bad spark at the plug end.  I really think that I have such an intermittent issue that it is almost impossible to see with the device.  It would be no problem if it was a solid fail.  I only have 2 EGTs one for cyls 1 & 3,  and one for 2 & 4.  The 1 & 3 side is the one that went high.  

I need to back up and rethink my very first test, share my findings, and ask for your help to determine if I provided the correct analysis.  Please bare with me for a moment.  My very first ignition system test was to swap the two horizontal ignition plugs, which in effect, swap the trigger coil input to the modules.  These are the easiest plugs to swap, as they are right on top.  As the result of that swap, I went from a bad running B ignition, to a bad running A ignition.  I may have incorrectly determined that this meant that the trigger coil circuit was good.  But I am not so sure.   Do you know?.  When you swap these two plugs and the condition moves, does that mean the the problem is before these plugs, or does it mean that the problem is somewhere further down the line towards that spark plugs?  This is so important and I am not sure if I was correct in saying that the trigger coil side was good.  I was looking for a troubleshooting guide, or flow chart that would definitely spell that out but could not find one.

I keep coming back to the trigger coils because of the intermittent nature of the condition and my thinking is that it could be as simple as a trigger coil air gap adjustment that is marginal.  To be honest, I think that this condition may have been there for a long time, and maybe since new.  I always felt that I had excessive vibration, but this is my only experience with Rotax.  The first thing that I must know is "Should I have seen the problem move when swapping these plugs" if the trigger coils were good?.............Tom   

If I recall, you have the 6+6 connectors.

The Trig Coil and the Mag switch are on the same connector.

When you swapped connections you also swapped Switches.

If the T-Coil was bad it would remain associated with the same switch.  No apparent Change.

Since the Problem DID swap, The problem is AFTER the connector.  I-Modules, I-Coils, Plugs, Wiring.

The EGT probe is NOT on cylinder 1+3, It is Either 1 OR 3,  I will assume #3,  Or commonly Both rear Cylinders, (2+3)

Sooty plug at idle is not uncommon.

Why #3 is clean is the question.

You are seeing #3s EGT go HOT during the misfire.

This could be because the unburnt fuel get ignited in the exhaust pipe and back-flashes into the cylinder burning the soot off of the plug. 

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Just to confirm we are on the same page...

Does this miss-firing issue only occur when operating with Mag-B ON and Mag-A OFF ???

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The problem appears to be associated with only the #3 "B" (Top) plug.  Very Strange!!!

To rule out the Plugs...

Do not Replace the plugs, but Swap the plugs in Cylinder #1Top with  #3Top,... and #1Bottom With #3 Bottom just to be inclusive.

If the problem moves to "A", suspect the now #1 Top Spark Plug.