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Discussion Starter #1 (Edited)
My Subaru has been making a slight rattle (like marbles scrambling) under light acceleration for the last month. Brought it in thinking it was exhaust and heat shield but they didn’t notice anything. Going to be bringing it in soon. Any ideas ? See comment below for reddit video (apologies for low quality)
 

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I have the exact same symptom & sound...light acceleration, bag of marbles but does not sound like valves rattling...a little less clunky than valves I think...just noticed it after my 60K kilometers service ($700CDN !!) which included a fuel system cleaning. They wanted $70 to clean the intake pipe? I respectfully declined. Coincidence? I think not. Please post any findings as I am sure the dealer will say it's 'normal'. SMH.
 

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The almost universal answer to your question and evidence is... detonation. Although I get no sound from your video, the camera is pointing directly at the engine, further supporting detonation as the issue.

It is easy and cheap to test this hypothesis... just fill up with the highest octane available with the tank low and drive under the same conditions as when you heard the unwelcome noise. Give the ECU some miles and time to relearn its tables.

Let us know what you find. I'm sure whatever you find that eliminates the sound will be valuable to others.
 

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Discussion Starter #5
I have the exact same symptom & sound...light acceleration, bag of marbles but does not sound like valves rattling...a little less clunky than valves I think...just noticed it after my 60K kilometers service ($700CDN !!) which included a fuel system cleaning. They wanted $70 to clean the intake pipe? I respectfully declined. Coincidence? I think not. Please post any findings as I am sure the dealer will say it's 'normal'. SMH.
Go figure... been having problems with my dealer too. Service packages are money grabs. I’m hoping it’s not serious. Appointment later this week and will report back.
I have the exact same symptom & sound...light acceleration, bag of marbles but does not sound like valves rattling...a little less clunky than valves I think...just noticed it after my 60K kilometers service ($700CDN !!) which included a fuel system cleaning. They wanted $70 to clean the intake pipe? I respectfully declined. Coincidence? I think not. Please post any findings as I am sure the dealer will say it's 'normal'. SMH.
 

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Discussion Starter #6
The almost universal answer to your question and evidence is... detonation. Although I get no sound from your video, the camera is pointing directly at the engine, further supporting detonation as the issue.

It is easy and cheap to test this hypothesis... just fill up with the highest octane available with the tank low and drive under the same conditions as when you heard the unwelcome noise. Give the ECU some miles and time to relearn its tables.

Let us know what you find. I'm sure whatever you find that eliminates the sound will be valuable to others.
Could be. I’ve heard of this happening in modern subies. It only calls for 87 in the manual yet I’ve heard of dealers recommending higher than normal to prevent the sound. How ridiculous. Will report back.
 

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In defense of Subaru... this happens in all cars and always has. I ride with my windows partially open year round. I hear it all the time to cars around me. It boggles me... the car is loudly letting them know it needs higher octane and they’re oblivious. I figure, stupid or listening to their manuals. “Not my problem.”

And it’s not just a “sound.” Google ‘detonation in cars.’

It won’t go Boom right NOW, but it’s like taking low doses of a poison. It won’t work right and WILL reduce power and gas mileage. Plus down the road the car will not be well off.

The cars of today are fighting owner cost projections and federal (and world) regulations. They’re forced to design them this way. As intelligent owners it’s our job to see through this mumbo jumbo... in not just cars but everything. Use your head; listen to the facts not the propaganda... your car is the horse’s mouth.

I have always used a higher octane than “called for” unless it called for 93, and even then different brands work better than others. I never want to have detonation in the first place.

Preignition is another animal altogether. It will kill an engine in a heartbeat. But that’s largely in forced induction cars and you dont need to worry about that.
 

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Discussion Starter #8
Hi all,

So I just heard back from the dealer. They replaced the PCV valve for free under warranty but suggested a terraclean service to rid all of the carbon build up (which was causing the rattle) - this is done during C service under fuel injectors I believe. Anyways, they weren’t willing to put that cleaning service under warranty so I argued for a discounted rate of some kind... they originally quoted me $250 - yikes. It seems odd that this car would have carbon build up with only 38,000 km. I’m wondering if people were into something about using higher octane gas even if the manual only requires 87.
 

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Discussion Starter #9
Second update: drove vehicle home and still a rattle noise... looked at the bill and saw a recommendation to fill up with premium gas (3 tanks and see if the sound goes away). Let’s see how that goes.
 

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Second update: drove vehicle home and still a rattle noise... looked at the bill and saw a recommendation to fill up with premium gas (3 tanks and see if the sound goes away). Let’s see how that goes.

Hi,

Was your issue resolved? Hard to tell from your video but my car makes a similar noise but I would describe it as a chain pulling. The dealer has replaced the timing chain etc but still are hearing the noise after several repairs. Curious to see if your issue was resolved.

Thanks,
 
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