02 engine clunk/tapping at idle & low RPM
 

2002 USA WRX What might cause clunking/tapping from the engine at idle & low RPM, goes away 100% at mid & above RPM. Sounds like from front of engine, driver side. Totally stock except exh. 200k mi. Worst when cold. Often goes away completely after warm-up. Been doing this for a while so it's not a rod or bearing, would have grenaded by now! Timing belt done by WRX pro <5k mi ago w all new parts. Car runs Great ! Bad lifter(s)? Recent synth change. Ideas? Help! Thanks!

piston slap

as above don't worry about it

Piston slap ?
 

Would it really go away at mid and high RPM if it was piston slap? I was guessing sticky or collapsed lifter pumping-up as oil pressure increases as revs increase....?

Yes it would go away at mid or high rpm. In my experience most scoobs slap a little, if you know what your listening for you can hear it. Again no biggie.

Piston slap ?
 

Hmmmm. Dunno. The knocking sounds pretty bad to me, don't think it's just piston slap. Mebbe I can capture an audio file but it would still be heard to discern the volume of the knock. Noises soooo hard to diagnose remotely !

"Often goes away completely when warmed up" Your words. Again, piston slap. Impossible to diagnose over the internet but I strongly would say its piston slap. If you don't know what piston slap sounds like the only way you are going to be happy is if you take it to a specialist and let them hear it.

Also piston slap can sound pretty alarming until you know that it is just piston slap lol

2002 WRX will have solid lifters not hydraulic.

As mentioned above, could well be piston slap taking into account the mileage the engine has done and the noise is from the drivers side, as it is usually Number 2+4 pistons which suffer from skirt bruising/slap.


Mick