6 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHIt's not always bore scoring (cat rattle, Fabspeed fix)
Leading reported evidence
Replace those
Performed · outcome unconfirmed
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1
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Read evidence and context
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Performed · outcome unconfirmed
The FabSpeed unit did put the nail in the coffin of the original O2 sensors, so replaced those after tripping a CEL, but smooth sailing thereafter.
It's not always bore scoring (cat rattle, Fabspeed fix)
Frequently discussed work
Recommend listening
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Suggestion
I have seen several engines replaced or disassembled mistakenly because of failing cats so I always recommend listening to the cats first for a thorough diagnosis
It's not always bore scoring (cat rattle, Fabspeed fix)
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Leading evidence: 'Replace those' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Recommend listening' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Performed · outcome unconfirmed · Original poster
I replaced with Fabspeed cat setup and it seemed to do the trick!
It's not always bore scoring (cat rattle, Fabspeed fix)
Recommend listening
Suggestion or failed attempt
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Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion
I have seen several engines replaced or disassembled mistakenly because of failing cats so I always recommend listening to the cats first for a thorough diagnosis
It's not always bore scoring (cat rattle, Fabspeed fix)
Replace got a sample analyzed, and continued driving/listening
Suggestion or failed attempt
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Discussions
Read evidence and context
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Suggestion · Original poster
Since I really didn't have much to lose, I did an oil change, got a sample analyzed, and continued driving/listening.
It's not always bore scoring (cat rattle, Fabspeed fix)
Use stethoscope
Suggestion or failed attempt
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Suggestion · Original poster
I narrowed the sound down to driver side cat using a stethoscope, and after I removed that cat to inspect it had a clear rattle.
It's not always bore scoring (cat rattle, Fabspeed fix)
Frequently discussed actions (5)
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Recommend listening
No successful repair reported for this finding.
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Discussions
Read evidence and context
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
I have seen several engines replaced or disassembled mistakenly because of failing cats so I always recommend listening to the cats first for a thorough diagnosis
It's not always bore scoring (cat rattle, Fabspeed fix)
Coverage and how to read this overview
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
6 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
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Generation: 20261027T060112Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Just wanted to throw a thread into the mix for those researching issues in the future.
I had my vehicle in for annual state inspection around 120k miles and it had no issues. However when I was pulling out of the garage I noticed a noise, sort of a rattle from the rear.
90% of the research led to bore scoring threads and videos, however mine was different.
I narrowed the sound down to driver side cat using a stethoscope, and after I removed that cat to inspect it had a clear rattle.
I have oil analysis done 2x per year and my numbers have always been solid, which is why I started looking for external causes (spark plug shields, loose clamps etc).
I replaced with Fabspeed cat setup and it seemed to do the trick!
Link below to video of before and after sound.
You Tube
Good video !! I have seen this before and mentioned it many times when people are trying to diagnose the ticking/knocking on M96 engines....
I have seen several engines replaced or disassembled mistakenly because of failing cats so I always recommend listening to the cats first for a thorough diagnosis
But that didn�t/doesn�t sound like bore scoring� It sounded more like a mechanical rattle not sync�d to the engine rpm (as bore scoring does). In any case, glad you got it figured out!
Agreed.
Initially I thought maybe plug shields since I recently did my spark plugs and coils. However, I did swing by a nearby Porsche dealer to check some cars they just got in, and I had a tech come out and have a listen. His words were "man, I haven't heard exactly that before.....sounds to me like bottom end."
Since I really didn't have much to lose, I did an oil change, got a sample analyzed, and continued driving/listening. Oil came back fine around the time I noticed the sound was most pronounced at driver side cat.
Hopefully this thread will save someone's sanity in the future
Same happened to me in May. Left cat was just old (both were the original OEM) and the rattling was attributed to the expansion of the cat itself. Went with FabSpeed, and considered Soul, but the back order for the latter was ridiculous.
Aside from the small notice in HP and torque, the real immediate feel was the loss of 11 lbs in the rear, and it made the car feel that much more balanced. The FabSpeed unit did put the nail in the coffin of the original O2 sensors, so replaced those after tripping a CEL, but smooth sailing thereafter.
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