Jump to content

Welcome to Ultimate Subaru Message Board, my lurker friend!

Welcome to Ultimate Subaru Message Board, an unparalleled Subaru community full of the greatest Subaru gurus and modders on the planet! We offer technical information and discussion about all things Subaru, the best and most popular all wheel drive vehicles ever created.

We offer all this information for free to everyone, even lurkers like you! All we ask in return is that you sign up and give back some of what you get out - without our awesome registered users none of this would be possible! Plus, you get way more great stuff as a member! Lurk to lose, participate to WIN*!
  • Say hello and join the conversation
  • Subscribe to topics and forums to get automatic updates
  • Get your own profile and make new friends
  • Classifieds with all sorts of Subaru goodies
  • Photo hosting in our gallery
  • Meet other cool people with cool cars
Seriously, what are you waiting for? Make your life more fulfilling and join today! You and your Subaru won't regret it, we guarantee** it.

* The joy of participation and being generally awesome constitutes winning
** Not an actual guarantee, but seriously, you probably won't regret it!

Serving the Subaru Community since May 18th, 1998!

Guest Message by DevFuse

- - - - -

Broken coil on 2015 Impreza - replace all four or just one?

Coil Impreza service

  • Please log in to reply
4 replies to this topic

#1 Tisorp



  • Members
  • Pip
  • 1 posts
  • San Jose, CA

Posted 13 March 2018 - 09:47 PM

I have a 2015 Subaru Impreza coupe.  The car has about 75,000 miles on it.  While driving home from work about a week ago, the car suddenly began driving very rough with the check engine light coming on in a flashing mode within 3-4 minutes.  I proceeded to drive directly to the local Subaru dealership, which was only a 5-10 minute drive away.


Upon performing a diagnosis, they informed me that one of the coils was bad.  As there are four coils, it raised the question of whether I should replace all four coils or just the one.  Here's what I learned from the dealership:


  • Subaru recommends replacing only the bad coil should one go bad
  • If a bumper to bumper warranty (or other warranty covering the coil) were in place and a coil went bad, Subaru would only replace the single coil
  • The dealership indicated that just because one coil went bad doesn't mean the other coils are any more likely to go bad than if they were on a different car which had similar mileage but never had a coil go bad
  • There is no recommended mileage at which the coils should be replaced
  • Coils cannot be measured for wear and tear.  E.g. it's a black & white thing - either it works or it doesn't work.
  • The dealer says the only real reason to replace all four would be for peace of mind
  • My driving habits or the service history had nothing to do with the coil going bad 

Based on this info, there doesn't seem to be any reason to waste the money to get all four replaced.  Is there any reason I should get all four replaced as opposed to just the one?


Thanks in advance for all feedback

Edited by Tisorp, 13 March 2018 - 09:48 PM.

#2 GeneralDisorder


    Elite Master of the Subaru

  • Members
  • 21,803 posts
  • Portland

Posted 13 March 2018 - 10:04 PM

Failure is rare. Replace only the bad coil.


#3 idosubaru


    Elite Master of the Subaru

  • Members
  • 23,874 posts
  • East Coast

Posted 14 March 2018 - 05:05 AM

Exactly. Replace 1, they very typically last the life of the vehicle.

Replacing all 4 for no reason is almost comical.

The old adage of replacing parts in sets is overplayed.

#4 kamesama980


    Advanced Member

  • Members
  • PipPipPip
  • 76 posts
  • Columbus, IN

Posted 14 March 2018 - 11:54 AM

3rd vote for just one.


there are things to replace in sets so they wear symmetrically or because of the effort involved: you don't replace one ring on one piston. you shouldn't replace one tire in a 4wd and many full time AWD cars.


Coils do wear out, the magnetic properties of the core change over time but the lifespan/degradation time of on ignition coil is so long and there's enough overhead before you'd notice that it's meaningless to the lifespan of the car as a whole. It's not even a consideration with the mean-time-before-failure calculation.

#5 keith3267


    Eat, Live, Breath Subaru

  • Members
  • 304 posts
  • near Memphis

Posted 14 March 2018 - 04:59 PM

Just one and use OEM.  If you replace with aftermarket coils that are not OEM suppliers, it would be possible to have them fail before any of the remaining coils go.


BTW, coils can be measured for wear and tear, but the test is really expensive and only done on large industrial distribution transformers, i.e. substation transformers.

Edited by keith3267, 14 March 2018 - 05:03 PM.

Also tagged with one or more of these keywords: Coil, Impreza, service

0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users