2010 Forester 40K miles Check Engine

In addition to check engine and cruise control indicator flashing, the engine runs very rough, no power, etc.

My wife was driving up a hill and had to pull over. I arrived, started the vehicle and drove it the remaining way home (barely). It stalled as I backed into the garage (on flat pavement).

I'm probably going to buy an ODB scanner at Harbor Freight for a diagnosis.
Good idea? Their scanner has good reviews for about $100.

I've read posts where a Forester displays check engine and cruise control but there is no complaint of engine performance. Mine definitely has poor performance. This came out of nowhere.

How many miles do you have on your car?

I do not know if you have Autozone in SF but in California Autozone reads codes for free.

As far as I understand any code reader will read your ECU for the fault code and you will be able to Google it.

Good luck,
Sam

Thanks for responding.

The car has 42K miles and the engine is an ordinary 2.5X.

I bought a scanner and the two codes are P0301 and P0302, cylinder 1 and 2 misfire. I've done some reading and found the ignition coil to be suspect but I'd like confirmation.

I've found posts where people have the same or similar codes to mine, P0301, P0302, P0303, P0304 but the engine isn't necessarily running rough or seeming to have a problem other than the codes. They change plugs and or wires, clear the codes, everything seems fine for days or weeks, then the often code reappears.

So, I'm wondering how the coil can play a part in this? A partially bad coil? Shorted output to two cylinders?

if its a turbo you have one coil per cyl and it would be unlikely for 2 coils to go out at the same time. if its not a turbo you can grab a old spark plug, pull #1 plug wire off your spark plug, put the other plug on it, set it on a metal part of the engine and see if you get spark when you crank the engine over or start it, repeat for cyl #2. if you have good spark to both cyl then you need to look into things like compression or bad injectors or wiring to them

Probably solved!

I pulled the coil and found case distortion and cracked potting on the section that feeds #1 and #2 cylinders, the same ones the fault codes referred to for cylinder misfire.

I'd like to upload pictures of the coil but the forum software is not allowing it for some reason. I try to upload <200k size jpg's but upload fails.
Any suggestions?

Next question is, why insist on a Genuine Subaru replacement coil when the first lasted only 42k miles?

YouTube user SCANNERDANNER has a video on Subaru coil testing. Try to search for it. I thought I added it to my Favorites but cannot find it at the moment.

As far as I remember the coil's resistance, as per FSM, suppose to be around 11 ohms, but I cannot recall whether primary or secondary.

Spark plugs should be changed every 30,000 miles. That also can be your problem.

Good luck,
Sam

Here we go:

https://www.youtube.com/watch?v=YBE7c7lfmnY

And one more:

https://www.youtube.com/watch?v=LdnnFD6J8Uo

Sam

That was one of the better instructional videos I've watched on Youtube. Thanks for sending.

I am an industrial electrician for 37 years and have seen many a bad coil that appear as this one does. I have no doubt the coil is bad.

I've tried again to upload two pictures of the coil that illustrate it has failed. Unfortunately, this forum's software will not allow me to upload two .jpg files, both around 170kb. I've tried from a windows 10 pc and a linux pc with the same result.

Here are two links to the photos via dropbox. You will see case distortion and a crack in one picture and cracked potting around the laminations in the second picture. Something bad happened inside.

https://dl.dropboxusercontent.com/u/73674915/SUBARU/coil1.jpg

https://dl.dropboxusercontent.com/u/73674915/SUBARU/coil2.jpg

WOW!

With only 42K on the engine. We can only guess what happened and why.

I am glad you fixed it!

Regards,
Sam

WOW!

With only 42K on the engine. We can only guess what happened and why.

I am glad you fixed it!

Regards,
Sam

I ordered a coil from Rock Auto. $70 less. 42k miles doesn't speak well for Genuine parts. Hopefully, I'll have it Wednesday.

I ordered a coil from Rock Auto. $70 less. 42k miles doesn't speak well for Genuine parts. Hopefully, I'll have it Wednesday.
I personally do not trust roach auto. They sent you wrong stuff and make you pay for the return.

Let us see what happens.

Good luck,
Sam

New aftermarket ignition coil delivered from Rock Auto yesterday (2 day priority mail seems to be the default). The coil appears to be sourced from the same production line that manufactures genuine Subaru coils, to my eye anyway.

I installed the coil and replaced all the intake air duct removed to create working space. Probably took one hour total, triple checking for loose tools, unconnected hoses, cables, etc.

Then I cleared the faults, started the engine and it runs fine! Back to normal.

I just wonder if I should buy another coil and carry it and a few tools. At 42k miles, I am assuming this was a random failure but I will be changing plugs and ignition wires soon.

Thanks for reading and the advice.

Don

I am glad your car is fixed!

Happy driving!