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Discussion Starter · #1 ·
What is the recommended mileage replacement cycle for ignition coils on a 2005 3.0 liter V6 engine? Thanks for any assistance.
 

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Given the amount of work required to replace the ones at the back, I personally wouldn't do it unless misfires are detected.
I'd replace them whenever you replace the spark plugs.

These are electrical components therefore there is no guarantee that replacing them is going to prevent them from failing.
 
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2004 Mazda 6s Wagon ATX
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What is the recommended mileage replacement cycle for ignition coils on a 2005 3.0 liter V6 engine? Thanks for any assistance.
Welcome to the forum!

I've been out of the 1st gen game too long - @DrFeelGood @GerryB or @TalonTsi90 you guys remember?
There is no "recommended" replacement for the ignition coils from Mazda.

The engine management system does not report mis-fires until they are severe, and catalyst damage happens with a barely perceivable mis-fire condition over time. Some users have been fine up to 100,000 miles. All 4 of my catalytic converters were destroyed at 110,000 miles. I got the dead catalyst (P0421/P0431) code and never got a mis-fire code.
I personally replace them every 60,000miles. The price of coils is $100-$200 dollars. The price of converters is $1000-$2000. What's it worth to you? All of that is assuming you do the work yourself.

@jman1200 and I have never agreed on this point but I do respect his knowledge, so, OP can take it as the other point on the opinion spectrum. For any other car this is generally solid advice. Rotate coil to see if it is bad then replace the faulty coil only. I would do that for all (and do, Honda Odyssey, Nissan 350Z) but this car it has been unsound for me.
 

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I've only got mild misfires once and I could feel the engine "missing power/hesitating". I guess it comes to how much you know your car and pay attention to its behaviour (not saying you guys don't).
IMO, replacing them often will help you sleep better but won't ensure there won't be any misfires. This is just me, I respect what others want to do and how they want to spend their money.

I guess to better answer this, would be by knowing how many cycles are expected from these coils.
 
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I've only got mild misfires once and I could feel the engine "missing power/hesitating". I guess it comes to how much you know your car and pay attention to its behaviour (not saying you guys don't).
IMO, replacing them often will help you sleep better but won't ensure there won't be any misfires. This is just me, I respect what others want to do and how they want to spend their money.

I guess to better answer this, would be by knowing how many cycles are expected from these coils.
I agree with you here. I can feel them very subtly but even now get thrown by the AC compressor sometimes. It was a nightmare to do that work (Mazda wanted $5700) the first time with everything rusted. Two hundred bucks every 12 years (my mileage rate) is cheap insurance (even given the fact that I have rarely received a faulty new electrical part)
Cheers @jman1200
 

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You can get coils for under $50, if they last you 3-4 years, its worth it. I got 6 with a lifetime warranty for around $35. Car died two years later, well the shop who worked on it where the mechanic quit during a timing chain/hg job killed it.
 

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Discussion Starter · #8 ·
All the feedback is much appreciated. We've only owned the car a couple of years. It's my daughter's car who is in college. PO indicated recommended schedules of work always done but had no records. Car appears to be in very good shape with 120K miles. I've opted to do plugs and coils since I'm not sure when they were done before, and for peace of mind.

Looks like a challenging job but very doable.

Thanks again for the feedback.
 

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My cats also started causing CELs at relatively low mileage (134k). The car felt a bit more sprightly after I replaced the coils, so I do think they degrade over time. Better to get fresh ones in there before they cause trouble with the catalytic converters.
 

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Discussion Starter · #10 ·
Replaced all spark plugs and coils. The job took about 3 hours. I made a list of all the steps after watching a YouTube video and reviewing my Haynes manual. It wasn't a bad job. I just made sure I tagged stuff as I pulled it off and then followed my list in reverse. Had a problem with one of the new coils. Advance Auto somehow had the wrong coil in one of the boxes. Next time I'll open and check all coils for consistency before I leave the store.
 

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My '06 started having misfires occasionally somewhere back around 155K miles, and my mechanic said it was the back bank of the V6 reporting the misfires. I had them replace the coils and plugs on the back side, but left the front coils alone. That solved the problem for a while, but then an occasional misfire would happen from the front bank, so I had them replace the offending coil up there. Based on this one data point, I'd expect to replace the coils around 150K - 175K, but obviously, your mileage may vary.

Getting at the back bank is a pain in the butt, but if you're handy with a wrench, you can do it. It's not a beginner job, but it's mostly just annoying, not truly difficult.
 

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As others have said, just change them when you do plugs.
A tip for removing the intake that I used was to slip a 3” long, 1/2” diameter vinyl hose over the intake bolts after they are all loose. It holds the bolts up out of the way and makes getting the manifold on and off easier.
 

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Replaced all spark plugs and coils. The job took about 3 hours. I made a list of all the steps after watching a YouTube video and reviewing my Haynes manual. It wasn't a bad job. I just made sure I tagged stuff as I pulled it off and then followed my list in reverse. Had a problem with one of the new coils. Advance Auto somehow had the wrong coil in one of the boxes. Next time I'll open and check all coils for consistency before I leave the store.
Did you check the coils before replacing them? Mine are all showing consistent resistance on primary and secondary windings so I wonder if replacing them will help at all.
 
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