Since I bought my Forester two months ago, I've noticed a noticeable engine tap upon first starting. You can hear it at idle when it's warming up for a minute or so, then it will be only noticeable under load. It definitely quiets down significantly once the engine warms up, but I can still hear a slight tap under acceleration with a warm engine.

She's got 223K miles on the original engine, so I'm thinking maybe some piston slap with possibly a little bearing wear in there? It's not a loud knock by any means (yet). Just wondering if  should be concerned at this point or just keep driving it until it gets worse. It is definitely related to engine temperature, and does seem louder upon starting in the cold weather that's now here. I'm running the recommended 5W- 30 oil.

My '98 Legacy EJ22 has had a very soft tap when I bought it that also mostly goes away when you drive it- I've always assumed piston slap with that one since the redesigned piston skits on the '97- '98 EJ22 seemed to be known for it.

Also, my son's 2001 Honda Accord 4 cylinder acts similar to the Forester- even though a much different engine. My mechanic actually checked bearing clearances and found them to be good. He attributed the tap to wrist pin clearance which he said Honda's are known for but not a major concern. I've never heard of Subaru's having excessive wrist pin wear though.

That engine is known for piston slap more than any other Subaru engine. Nothing you can do but knurl the skirts. 

GD

Stevo F,

The subie piston slap issue occurs as you describe in these older engines. My 97 OBW LTD had the issue as well and I just lived with it.

Years of forum posts and research shows, that while annoying, piston slap will not affect the engine's longevity in any way. My 97 had it, but not my 2002, my 2007, my 2012 or my present 2017. Some humourously suggest to just turn up the radio.

Piston slap. Ignore it and drive it. 

my 2002 Forester sounds like hell when it is cold - rattles something awful.. but once warmed up it is fine - 244,750 or so right now..