Subaru Missfire

[Bob Kontak]

Sister's 2005 Outback Impreza Sport wagon. Running rough. Big missfire(s).

Basic 2.5L NA engine.

Pull plugs. Every one is bathed in oil past where the boot plugs on in the tube.

Valve cover gaskets/seals gone.

You think this might be a problem?

[porsche tech]

I'd guess coil pack...plug doesn't look fouled. Just a guess.--Dave

[DonDavis]

Yup, I think you nailed it. Replace the plugs, plug wires and coil pack.
Replace the valve cover gaskets with factory new ones. Take your time with the gaskets. They are directional, closely inspect the old ones for tiny lines, compare to your new factory gaskets. And please properly torque the cover bolts.

I bet it’ll run great after that.

[gordner]

On the 2.5 na for sure it is common to have oil bleed down the plugs, the valve cover gaskets suck.
All of the above absolutely in the nail.

[unclebilly]

That is the issue.

[Bob Kontak]

Originally Posted by unclebilly

That is the issue.

Yepper! Told my beer drinking pal "I am going to post this because many of these guys know these cars better than me."

I have replaced the four cluster coil unit, plugs but not wires.

Should have as the rubber boots, similar to the old 911's but not a hard tube were extremely floppy. Tired and played. Car was way smoother but under acceleration, some missfire again.

Remediation is short term without valve cover gasket fix.

[Oracle]

All subaru's engine sound like they misfire... (at least to me)
and the heads all crap out, they are made to make you spend sooner or later and question yourself why did you get that car in the first place..

[SCadaddle]

Originally Posted by DonDavis

Yup, I think you nailed it. Replace the plugs, plug wires and coil pack.
Replace the valve cover gaskets with factory new ones. Take your time with the gaskets. They are directional, closely inspect the old ones for tiny lines, compare to your new factory gaskets. And please properly torque the cover bolts.

I bet it’ll run great after that.

Agree 100% with this, and that's from currently owning a 2005 Legacy with the 2.5 2 cam engine and a pair of older Legacy's with the 2.5 4 cam engines.

On the 2 cam 2.5 engines the "spark plug boot" between the spark plug tube and the valve cover over time become hard as a rock and fail to seal the spark plug tube from the oil in the valve train. It's a pretty easy job and use all new grommet seals around the bolts (5 per side more than likely on that engine) a pair of new spark plug boot seals and a new valve cover seal. Just have to be real careful putting the valve cover on, try going straight on with it so you don't fold or misalign the spark plug boot seals by moving the cover up and down when putting it on. Great time to check the valve adjustment while you are there.

[SCadaddle]

Spark plug tube seal.





Original 89k mile 14 year old spark plug tube seals, one that was misaligned by the factory from the beginning. Both hard as a rock.

[SCadaddle]

Inside of valve cover. Note where the spark plug tube seals seat. That's why you don't want any up-down movement when putting it on or you will deform the seal.

[cabmandone]

The Impreza I bought for my daughter had a light show going on at the coil pack when it was dark out. Car was running like crap. Replaced the wires and did plugs while I was at it and it ran like a top. Yeah.. those valve cover gaskets suck and others have pointed out the plug seal. And for all the gripes... I still miss my 95 Legacy wagon (ATV with air)

[DonDavis]

Such great information!

My '96 Legacy Outback 2.2 SOHC wagon has 312,000 miles and runs like a top. I stumbled into owning this beast for $600, did a BUNCH of regular maintenance and upkeep and it's the bee's knees.
I'm in it for less than 2k. Such a cool car.

[Bob Kontak]

Originally Posted by SCadaddle

Inside of valve cover. Note where the spark plug tube seals seat. That's why you don't want any up-down movement when putting it on or you will deform the seal.

Do you have lift the engine at all to perform this maintenance? Meaning up off the motor mounts a few inches?

[fastfredracing]

From what I remember , one of the rear lower bolts is a sob, and lifting the motor a little bit makes it much easier . I just cannot remember if this was a 4 cyl, or 6 cyl car . I do remember spending a lot of time turning just one valve cover bolt .
Good luck Bob !

[Bob Kontak]

Originally Posted by fastfredracing

I just cannot remember if this was a 4 cyl, or 6 cyl car . !

4 cyl 2.5. Thanks for the info. I did see one vid on a newer version where bunches of auxiliary stuff had to be removed for access but it still boiled sown to one or two stinker bolts.

[Bob Kontak]

Originally Posted by Bob Kontak

I have replaced the four cluster coil unit, plugs but not wires.

Replaced wires Saturday. Smooth running engine now but she probably has three days until the plugs drown again.

[VincentVega]

Originally Posted by fastfredracing

From what I remember , one of the rear lower bolts is a sob, and lifting the motor a little bit makes it much easier . I just cannot remember if this was a 4 cyl, or 6 cyl car . I do remember spending a lot of time turning just one valve cover bolt .
Good luck Bob !

x2 I dont remember the year, maybe late 90's? Doing valve covers on one almost had me giving up my tools.

[cabmandone]

I did valve covers on a 2.2 and it wasn't a terrible experience. And to be honest, pulling a 2.2 or 2.5 is about as easy if not slightly easier than dropping the 3.2 out of my 911.
Did a little surfing. The link below covers Timing belt and valve cover replacement. Ignore the tb info and just grab the valve cover info.
https://www.subaruoutback.org/forums/99-do-yourself-illustrated-guides/26199-2001-timing-belt-water-pump-valve-cover-gasket-set.html

[gordner]

I changed my impreza engine, pulling it for the first time, alone, it was on the floor in less than two hours.

[Bob Kontak]

Thanks for the info, guys.