Need help. No power getting to ignition coil

[audi_monne]

C5 a6 2.7t. Engine was misfiring, I found the cylinder that wasn't firing. Checked the coil, coil is fine. Must be that there's is no power getting to the coil, how do I proceed??

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[62willys]

How'd you check the coil, swap it with another cylinder? In my experience, you need a systematic approach to solving misfires. Do you have a vag-com to log misfires for each cyl. And total count? If you do, figure out which cyl is the "best" and swap the coils from best to worst cyl's. Run engine and monitor measuring blocks. Note any change. Do the same with plugs, swap, monitor, and note change. If your results for the plug swap are inconclusive, go buy decent COPPER plugs. They are only like 2$ a piece and copper is a better electrical conductor than platinum or iridium. They only last a few thousand miles if you leave them in there but they're great for diagnostics and racing applications.
Next move to the coil harness. Check for resistance on the common grounds and look for breaks in the insulation. These wires are constantly heat cycled and as a result are prone brittleness. A continuity test isn't enough here. Look really good at every wire till it clears the heat effected zone and use a multimeter to find any faults.
If still no change, swap injectors with a cylinder that has no misfires. Again, run motor, monitor misfires for all cyl's, record results.
If still no change, it's time for a compression and leak down test.
Good luck

[audi_monne]

How'd you check the coil, swap it with another cylinder? In my experience, you need a systematic approach to solving misfires. Do you have a vag-com to log misfires for each cyl. And total count? If you do, figure out which cyl is the "best" and swap the coils from best to worst cyl's. Run engine and monitor measuring blocks. Note any change. Do the same with plugs, swap, monitor, and note change. If your results for the plug swap are inconclusive, go buy decent COPPER plugs. They are only like 2$ a piece and copper is a better electrical conductor than platinum or iridium. They only last a few thousand miles if you leave them in there but they're great for diagnostics and racing applications.
Next move to the coil harness. Check for resistance on the common grounds and look for breaks in the insulation. These wires are constantly heat cycled and as a result are prone brittleness. A continuity test isn't enough here. Look really good at every wire till it clears the heat effected zone and use a multimeter to find any faults.
If still no change, swap injectors with a cylinder that has no misfires. Again, run motor, monitor misfires for all cyl's, record results.
If still no change, it's time for a compression and leak down test.
Good luck

Wow thank you so much! I posted this a while ago hoping for anything helpful but was about to give up. Thanks I appreciate the extensive answer!

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