99 Legacy. EJ22. Auto. @ 2000 rpm +/-, I have a rattle that only comes when driving, lower in the RPM range with light throttle that sounds a lot like a 350 Chevrolet when the timing set is too hot.  Recently replaced plugs (yes, NGK 2756), coil, wires front O2 sensor, timing assembly. New calipers both front. Owned like 5 1999’s, have mostly rebuilt them all, never heard this sound before. 

Driver front CV shaft both boots are bad and throwing grease, but doesn’t make noise when wheel is at full lock and moving forwards or back, left or right.

Ball joints and tie rods are tight. Can’t find a loose beat shield. Driveshaft seems in great shape. Wheel bearings are smooth. No CEL. Even swapped good knock sensor for another good knock sensor. Idler pulley for compressor belt is smooth and silent as are the others. I’ve taken the timing cover off twice now since the job to see if the problem is in any of that system but only find that all is operating smooth. Cannot recreate sound with parking brake and foot brake held with trans in 1, 2, 3, or D. Cannot recreate sound in park. It only happens when in motion. Only with light throttle or when I let off and come back on throttle easy....also more pronounced on incline. Car goes to full throttle smooth and comes down smooth to idle. Starts good. 

Going to try decarbonizing via sea foam today.... CV shaft is out a few days as I’m in Alaska. 

Ideas? I can’t find any videos of spark knock in a Subaru but I can’t imagine it’s muxg different. 

Can the CV joint cause this kind of sound? If so it’s a new sound to me. Thanks for lookin

 

older soobs sometimes have bad knock sensors with no code. One of the few sensors where cheap ebay units have worked OK for a lot of people.

but, it usually fails by pulling timing so.....?????

Subaru heat shields are notorious for rattling.

And your symptoms (low RPMs, light-load, decelerating) seem to point at heat shields.

BUT, heat shield will also rattle with the car stationary.  And the rattling can be quite loud when the engine is started.  If you cannot create the rattle at zero speed, then it is most likely not the heat shields.

Muffler - internal parts moving or beginning to collapse. 

A mate of mine had the same thing in his forester last week, but a dull thudding sound like the exhaust was hitting something or there was something wrong with the rear diff (mate’s first thoughts).

We narrowed it down to the exhaust. He took a punt on it being the rear muffler and had it replaced. No more noise. 

The sound was most prominent between ~1900 to ~2100 rpm. Loading the engine up could make it louder the longer he let it go before taking action. 

Cheers 

Bennie

I have a video of the sound but can’t upload help me

Upload to YouTube then post link if you cant directly uplpad it here.

 

you say you replaced wires - but with what?

Subarus are finicky about plug wires - OE or NGK ONLY!

It has been proven time and time again that parts store wires are no good on a Suby. They might be fine for many applications, but Subaru is not one of them.

 

0:03.

You can hear my pen moving and hit something almost immediately upon video start, sorry. 0:03 tach drops below 2k and I bump the throttle +2k and it makes the noise. Sometimes under the right, consistent load- it’s near continuous. Arrhythmic in nature, not hitting every revolution type thing, but close. Like a TBI 350 pinging! If I’m going uphill and feather it +/- 2000RPM I can get it to make the noise almost every throttle blip which is what got me thinking belts and pulleys....it’s metallic but there’s almost a ‘tweet’ with the noise that the camera doesn’t so much pick up.

 

Ive since removed the A/C belt to rule out those pulleys, checked over fascia for loose parts, checked/secured all heat shields again, checked all flywheel bolts through access port, went over brakes and bearings, tie rods, CV shafts (bad exterior boot on DF, but doesn’t make any clicking noises at full lock). Motor mounts look good. Tranny mount looks good. U joints are all tight, support bearing looks/feels good. Fluids good in rear diff, gearbox and trans. No chunks, ATF passes white paper and smell tests, proper trans filter.

 I can’t reproduce the sound in park, or in drive with brakes held, or on jack stands in any capacity. I’m lost! Seems to be getting a bit worse but slowly. Lots of miles in Chugach mountains daily here, so I hear it a lot and my sanity is waning. A ‘ride-along’ with a Subaru tech here on the last frontier is 2 months out, I don’t trust those guys any farther than I can throw my 60” pipe wrench, anyway.

 

NGK wires and wouldn’t dare use anything else.

Edit- Clarity

Edited June 21, 20196 yr by joomanburning

BETTER VID bump. Went over everything again I cannot find this noise

 

A lot better. I swapped knock sensors also to see if the one I had installed was malfunctioning and ‘missing’ whatever the noise was... still no CEL outside of a poltergeist EVAP440 it’s always had

Edited June 24, 20196 yr by joomanburning

loose sway bar endlink?

Tight as I’ve seen them on any other Subaru 

I have the same mystery rattle. Only occurs during slow speed acceleration. I read somewhere that it is probably "piston slap" common on high mileage ej22's (mines at 198k). It's annoying and worrisome - at least for a paranoid freak like me. 

Wish there was someway to know for sure, as I rely on mine for daily driving. 

actually, piston slap only occurs when the engine is cold, and disappears once the engine is at full operating temp - and it is more common on the early EJ25s (more specifically EJ251, for sure - i have an 02 Forester that has piston slap), not the EJ22

does a 99 have the 'new style' timing belt tensioner? They can mimic rod knock. Though, I'd think you could get the sound while idling.

Is your sound ONLY when moving?

That “new” piston in arm tensioner does the knocking noise all the time, some you can see the tensioner bouncing up and down with the cam cover removed. Ours required a stethoscope to properly diagnose as it passed the visual inspection. 

The other thing that could be rattling is the dust cover under the bell housing. 

Cheers 

Bennie

Yes only when moving I cannot re-create it on jackstands or sitting still with the brakes held.  

 

I had started to wonder about that tensioner

must be driveline or suspension then.

cv joint clicking will sometimes be 'quick' - 6 times per wheel rev.

if clunking from inner joint, usually more like once per rev.

 

the above are rough guidelines of course. Is it uneven when it occurs or repetitive?

 

gonna throw this out there - maybe way off base, but then again, maybe not..

worn out/torn bushing or mount somewhere?

I watched your video, did not hear any "rattle", but did hear what sounded to me like a "thunk" at one point.. without actually being in the car it is really hard to tell

9 hours ago, 1 Lucky Texan said:

must be driveline or suspension then.

cv joint clicking will sometimes be 'quick' - 6 times per wheel rev.

if clunking from inner joint, usually more like once per rev.

 

the above are rough guidelines of course. Is it uneven when it occurs or repetitive?

 

Uneven during throttle bump or certain areas around 2k if on a light uphill grade. I’m going to upload a better video.

its the outer boot that’s torn. And I think your right I should be able to recreate on jack stands or stationary, or with brake held if it’s the tensioner.

Edited July 23, 20196 yr by joomanburning

When I bump the throttle, almost squeaky sounding 

 

Edited July 23, 20196 yr by joomanburning
Melvins

check rear bushings on the front lower control arms.

end links for sway bar OK?

 

kinda wonder about the u-joints now too.

 

I’ve checked the ujoints and carrier, one of the first things I went for. Solid, no play.

Now it’s exhibiting BOGTHROTTLE

thanks from Alaska for bearing with me thus far. 

Edited July 23, 20196 yr by joomanburning

Any suspension mount bolts loose? 

Engine mounts loose or broken? 

20 hours ago, joomanburning said:

I had started to wonder about that tensioner

Tensioner noise will be there from start up and may get louder with revs, so you can rule that out. 

Cheers 

Bennie

On 7/23/2019 at 5:47 AM, el_freddo said:

Any suspension mount bolts loose? 

Engine mounts loose or broken? 

Tensioner noise will be there from start up and may get louder with revs, so you can rule that out. 

Cheers 

Bennie

I checked to humor myself it’s definitely not the tensioner, anything of that nature would very likely be present regardless of drivetrain engagement. But I asked for advice and dangit if you ask, you better at least heed otherwise favor gods will anger.

I’m really leaning to CV or trans issue