Over the past month I noticed some increasing misfiring, a random CEL turning on and off, increasing roughness, and then finally a flashing CEL with severe misfiring. Scanning with my OBD-II revealed a cylinder 3 misfire. In the processing of identifying the issue I checked for spark at the coil pack by removing the plug wire and checking for arcing. Cylinder 3 had no spark whatsoever and completely removing the wire didn’t change the severity of the misfire. I swapped the plug and wire from cylinder 1 to 3 but the problem of no spark remained confined to cylinder 3. Thinking the issue might be the coil itself I temporarily put on a brand new coil pack but the problem persisted (and I returned the pack for a refund). I finally searched these boards and found posts where one cylinder lacking spark was often traced back to the igniter. Neither Auto Zone and Advance Auto Parts had this part in their systems but O’Rilley did. I limped over on three cylinders and in their parking lot quickly swapped it out. The change was dramatic and amazing! No more misfire and, better yet, the engine seems happier and more responsive than ever. I’m wondering how long the igniter was failing before it caused an outright misfire.

 

Sharing this here in order to help others and also find out why I’ve never heard of igniters on other makes going bad.

 

Cheers.

Edited January 12, 20188 yr by bstone

You had probably the rarest part failure that a Subaru can have. I've replaced one. It failed because someone unplugged it and lost the rubber grommet seal that's in the connector. Moisture got in and all the pins rusted together. Other than that I think I've only ever heard of one or two actually failing due to an internal problem.

 

Why don't you hear about it in other makes? Other manufacturers call it an ignition control module, and they die all the time. Better part is that most of the time when they conk out on other vehicles, the engine doesn't start at all.

Thanks for letting us know.  I didn't know there was a second part to the coil!

still don't understand how you could have spark on Cyl 4 but not on 3.  They are paired at the coil.  The igniter doesn't differntiate between the pair.  It's signal to fire the coil should drive both 3 and 4 as a pair.

 

Glad you got it fixed but I might suggest that the Original coil may have in fact been bad.  I have seen a few fail in this way. Once on my own car, Spark at No. 1, but not at No. 2.

It was probably only running on two cylinders. The computer just isn't smart enough to throw 3 and 4 misfire codes under some circumstances.

 

GD

still don't understand how you could have spark on Cyl 4 but not on 3.  They are paired at the coil.  The igniter doesn't differntiate between the pair.  It's signal to fire the coil should drive both 3 and 4 as a pair.

 

Glad you got it fixed but I might suggest that the Original coil may have in fact been bad.  I have seen a few fail in this way. Once on my own car, Spark at No. 1, but not at No. 2.

It also made little sense to me but when I pulled the wire from cylinder 4 it had spark. I have an inline spark tester with a clear chamber and the spark looked normal in all but cylinder 3. I don't know how to explain it.