Rattling Valves

[NTIMD8R]

As the weather started cooling down in October I started noticing a new sound from my '04 Mazda 3 2.3L engine upon acceleration that sounded like rattling valves. I had been running 87 octane gas for a long time now for better fuel mileage so I switched to 89 octane thinking that might help. It didn't.

The rattling is more prominent when the engine is cold. It never rattles at idle, however, it will under almost any amount of acceleration until the oil heats up to around 160-170 degrees. Then the rattling is heard only under moderate to heavy acceleration.

The engine has almost 140,000 miles on it and still runs strong with great oil pressure. Mobil 1 oil and filter used since I bought it with 28,000 miles on it. A knowledgeable racer thought that maybe a weak valve spring was causing the noise. But if this were the case wouldn't it also rattle at idle?

This one has got me stumped... Anybody have any ideas on what could be the cause? Any help is greatly appreciated!

 

[djltoronto]

A video with sound will help a lot for this one.

 

[NTIMD8R]

I do not own a video camera. However my wife's point-and-shoot Canon does take video w/sound--not HD but hopefully the sound quality will be good enough to be able to hear the rattling. Will do my best...

UPDATE: Was out driving today in 15 degree weather. Once the oil warmed up to 150 degrees I really didn't hear any rattling/clacking at all, even under hard acceleration. Maybe it still was but I couldn't hear it like I normally do over the sound of the engine revving.

 

[NTIMD8R]

Alright, now I feel stupid... After months of trying to figure out how to solve my "rattling valve" problem, I FINALLY have solved it!

I had a CEL go on last week. The Dashhawk told me it was an "insufficient coolant temperature" problem. This was new to me. Heard of overheating, but running too cool?! Probably a sticking thermostat (I've since reset the light and it hasn't come back on).

Anyway, I popped the hood to check out the water pump for any leakage and noticed that the top mount of my Weapon R engine torque damper had almost completely unthreaded itself out of the top of the damper body! At the bottom of the damper piston, where it attaches to the engine mount, had loosened itself too. I placed my hand underneath it and lifted. The whole damper pretty much just flopped up and down in my hand! I tightened everything back up and the next time I drove it I noticed that there wasn't anymore rattling--NONE AT ALL!! Verified it again the next morning when everything was cold--still NOTHING!! Woo Hoo!! Problem solved! A BIG relief being that I was thinking I might soon have a blown engine on my hands! A ruined ETD is much cheaper than a ruined engine!