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Discussion Starter · #1 ·
I have a 2015 mazda 6, it has been occasionally throwing a multiple cylinder misfire code and then a cylinder 2 misfire code sometimes as well. I've changed the plugs, wires, and core packs. It didn't fix it, I put a bottle of Redline injectior cleaner in and the codes went away for a few months. Now the cylinder 2 misfire code is back and the cleaner isn't helping this time.

Any ideas on my next step?
 

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Check condition of the plug in hole #2.
If ok, swap THAT coil pack and only that one with another hole (e.g. #3)

If the misfire moves then the coil pack is bad.

If it does not move then the implication is that either (1) the wiring is toofed (you hope), (2) the injector is toofed or (3) the engine is internally toofed (e.g. valve sealing, etc.)

Injectors are not fun to change on DI engines.

How many miles on the car?
 

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Discussion Starter · #3 ·
There is 165k on the car. We bought 4 new coils and when we changed them out the car started running really rough so we put the old ones back on and took the new ones back. It only misfires when it cold starts during the high rpm warm up. It purrs like a kitten any other time.
 

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Ah, where did you get the "new" coils?

I'll bet you have one bad coil pack and possibly one bad plug. Switch the coil pack (and plug if you want) for that cylinder only to one of the others and see if the misfire moves.

If it doesn't then you have removed those two items from the potential fault list. Throwing parts at a problem is usually a mistake.
 

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It only misfires when it cold starts during the high rpm warm up
Thats not a misfire, its on purpose to warm the cat up faster.
 

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If its the "Raspy" thing then yes.

But, Forscan gives individual misfire counts and one thing I've noted is that when cold (and at idle) you'll get counts when the plugs get a bit old that go away with new ones -- even though they appear to be entirely serviceable (and, frankly, are.)

The PCM is sensitive enough to pick it up, however...
 

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If its the "Raspy" thing then yes.
My point is, if it doesnt misfire any other time, then its attributable to the timing adjustments and high valve overlap. But, with 165k the plugs might not have ever been changed.
 
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