I have a 2009 xD, second owner since 2015, has ~165k miles on it. I’ve really enjoyed it. I’ve taken it to the same local mechanic since 2019 or 2020.

Since 2020, I’ve had ignition coil failures in all 4 positions at least once, and on #3 I think 3x, last time 13 months apart (I drive it 1-2 times a week).

The mechanic concluded it was a rash of bad parts. All the failed coils have been under warranty, and he’s replaced them without charge. Recently he replaced #3 again, and it seems to be running OK now, as I can't sense occasional misfires and no code has registered (I've gotten kind of sensitive to that feeling prior to the total loss and rough idle).

I discussed it with the mechanic, that when I drove it, I might have flogged it a bit to go up some steeper hills, and he suggested taking the cover off the engine to let #3 cool down more. I'm driving it gently now.

However, I remember that after one of the coil losses, I drove it on 3 cylinders + misfiring cylinder maybe 40 miles.

Did I damage the engine by driving it 40 miles while misfiring? Is that reparable, or would that mean a new engine, or…what do you think? What do you suggest I do next?

At this point, it doesn’t seem reliable, as I never know when I’ll start sensing misfires or lose a coil. The dealership would charge $170 minimum just to check if their tools can detect any misfires, then take things apart to diagnose the problem, etc.

 

were the ignition coils OEM?

 

Just talked to the mechanic. None of them are OEM, but they are all "OEM quality", not the cheapest ones. They all came from a NAPA auto parts store.

 

I had looked into the topic of ignition coils before, and a lot of people were saying to avoid new 3rd party and buy used OEM, as there were many problems when buying non OEM. IIRC Denso was the OEM brand. As for driving while the engine is misfiring, I looked into this before as well, and when that happens it is best to take it off the road ASAP, so you may have done some damage driving it that far with a misfire.

 

Thank you.

 

Yeah, I'm going to say it's highly likely they're not 'OEM quality'...mechanic's not going to tell you he used the cheapest available at NAPA, which definitely doesn't carry the same quality of parts they once did, and that's why they're failing. One thing I have learned is with electrical stuff you are usually far better off going with OEM parts. The original coils sound like they got you 100k+ miles, so why not stick with them. They will be more expensive but you shouldn't find yourself replacing one or more of them very six months or so.

And watch out for counterfeit parts on places like eBay and Amazon, if the price is a huge amount cheaper than OEM prices there's probably a reason. I know in the Lightning world, OEM Motorcraft coils are usually the 'go to' and a bunch of guys were buying them off Amazon for 1/2 the price and they turned out to be fakes.

 

Thank you. Yes, Mr. Mechanic advised me not to buy the cheapest parts, cautioned me against amazon etc.
Do these look somewhat trustworthy? It claims DENSO...would that be printed on each coil?
https://www.sixityauto.com/4-pc-dens...056073784.html

I could buy that set of 4, then ask original Mr. Mechanic to replace all of them without charging me labor? Is that asking too much?

 

They're $63 each at Rock Auto for Denso coils, so $250-ish...less than what you're looking at above.

It's four bolts and electrical connectors to replace them, although there might be an engine cover that needs to come off, but nothing someone with even a basic knowledge of DIY couldn't do.

 

Thanks!