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  #1  
Old 07-23-2007, 11:36 PM
Cudadrag Cudadrag is offline
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Default MSD 6AL failure?

My trusty Duster has just now developed a major mis in the engine. All plugs changed, plug wires ohm'd ok, Coil ok, All cylinder's compression is ok, No intake or head leak detected but mis continues. If not getting worse. It appears to be spark related but nothing seems wrong. I have had one MSD 6AL box go bad but that box just stopped working.

My question is: Can the box develop irregular firing and cause such a mis? I'm going to have the pro shop check the box and distributor but would like to know if others have seen a box do this?

THANKS!
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  #2  
Old 07-24-2007, 02:26 AM
cudabob496 cudabob496 is offline
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Could be the box, but is distributor okay, and are the plug wires actually connected to the spark plug inside the boots? Disconnect vacuum advance to see if problem goes away.
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Old 07-24-2007, 08:41 AM
BJSracing BJSracing is offline
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Do you have a rev limiter chip in it? If so I would pull it out and see it the problem still exists. I have had a bad chip that would cause an irradic misfire. Don't know if that is the case with yours or not but hey it never hurts to check it out.
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Old 07-24-2007, 12:36 PM
Cudadrag Cudadrag is offline
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Yes I do have a chip right before the 2-step chip. I will take them out of the loop and see if there is improvement. The new plugs are showing they are firing just not quite in sync.
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Old 07-24-2007, 12:42 PM
mhenesian mhenesian is offline
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Hi Cudadrag,

Check the grounding of the MSD Box (that is the black ground wire, not the box itself). MSD ignitions require a very low resistance ground. Wire brush, new screw, add a serrated washer, etc... Also, I've had EMI problems with plug wires running on top of or crossing over the MSD trigger wires causing mis-fires. Very frustrating, also the "crimp connectors" that come with the MSD ignitions can also go bad after awhile, causing intermittent triggering problems, etc...

We also have had two oil filled MSD Blaster coils and one Accel coil fail on one vehicle due to excess vibration. Got replaced with the MSD epoxy filled "off road" Blaster coil,

Mark Henesian

(above comments come from actual road/track experience trouble shooting a number of MSD units)
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Old 07-24-2007, 06:47 PM
cudabob496 cudabob496 is offline
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My money is on the the distributor.
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