Forester Low compression

[Royoutdoors]

Hello guys,
Getting cold here in western Colorado! 14 f.
So developped a miss fire cylinders 2 & 4.
Checked spark- good. Checked injectors-good, checked compression- 1 & 3 165& 168
2 & 4- 110 -115.
Timing, valves, or just 288,000 miles??
Thoughts?
Thanks, Royoutdoors

 

[Ratbag]

Bugger.

Probably rings, valves or head gasket/s.

At that mileage (~463,000 kms), probably piston rings and exhaust valves.

Have you used upper cylinder cleaner routinely at every service?

 

[Kevin]

Was the test on a warm engine? Definitely see an overhaul in your future.

 

[Royoutdoors]

Yes warm engine, head gaskets & timing set at 202,000, about 3 years ago.
Never used upper cyl. Cleaner.
Going to look at timing belt, did develop an oil leak under timing cover about 2 months ago make sure that didn’t do something to cause misfire but yes overhaul or lower mileage salvage is in my future

 

[Ratbag]

Never used upper cyl. Cleaner.

That is almost certainly the root cause of the problem.
It should be used at EVERY service with Subarus.

Going to look at timing belt, did develop an oil leak under timing cover about 2 months ago make sure that didn’t do something to cause misfire but yes overhaul or lower mileage salvage is in my future

Trust me, you would know if you have a timing belt problem.
All Subarus (AFAIK) are interference engines. A timing belt "problem" would almost certainly destroy the engine.

 

[Royoutdoors]

That’s what I heard, overhaul is a good way to learn about Subaru engines I guess,
Overhauled lots of Chevys, fords,& a couple Cummins. Be 1st Subi.
Thanks for the input, wish me luck

 

[Royoutdoors]

What kind of Cleaner should a guy use?
I haven’t heard of doing that before

 

[ateday]

Sometimes called Upper Engine Cleaner, plenty of tutorials on YouTube. Some good, some ??
I use it and I think it works FWIW.

 

[Ratbag]

@Royoutdoors ^ It's called "Subaru upper cylinder cleaner" or similar.
Most importantly, it also cleans the MAF/MAP sensor in the intake manifold. It is this sensor which determines how rich/lean the engine should be running on any given cycle, in real time. It's kind of important!

 

[Royoutdoors]

Thanks, I’ll have to check into it

 

[Royoutdoors]

Update..put air in spark plug holes on 2 & 4,
Loosing it out the exhaust!
No intake leak, no crank case leak just exhaust so maybe an adjustment or valve job and can run her another 100,000!
Pulling valve cover now will update again when I figure it out

 

[Royoutdoors]

HAPPY DAY!
Exhaust valves tightened up for some reason,
Getting worn I suppose and lost clearance.
Purrrrs like a kitten again!

Thanks for the input.

PS. Got some sea foam upper engine cleaner, smoked pretty bad for a bit so must have done something for it,
Good for another 25-30,000 then timing belt time

 

[subyroo]

Sea Foam or Upper Engine Cleaner at every service is good for your Subaru.