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YOUR RESEARCHDifferent Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Leading reported evidence
Clean maf (which was dirty) and have not seen codes
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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0
Unsuccessful attempts
1
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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.
Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
I cleaned the MAF (which was dirty) and have not seen codes for a while.
Different Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Leading evidence: 'Clean maf (which was dirty) and have not seen codes' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'small vac leak' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check fluid levels regularly' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
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.
Discussions that performed work without a confirmed outcome
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Performed · outcome unconfirmed · Original poster
I have replaced all the sensors about 5 years ago.
Different Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
small vac leak
Suggestion or failed attempt
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0
Identified cause
1
Suspected cause
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Reported fixes
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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.
Discussions that suspect a cause
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Suspected cause
If it's only with cold startup at idle, it's likely a small vac leak.
Different Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
Check fluid levels regularly
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
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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.
Discussions that contain suggestions
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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.
Different Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
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Unsuccessful attempts
1
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.
Discussions that contain suggestions
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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.
Different Smell from Hot Engine - Cats? - 986 Forum - The Community for Porsche Boxster & Cayman Owners
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.
986Forum: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T152433Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
I recently had CEL for drivers side air sensors, they were not persistent, but periodic, cleared them with Duratec. I have replaced all the sensors about 5 years ago. I cleaned the MAF (which was dirty) and have not seen codes for a while. But I have noticed a different smell after driving the Boxster S plus a new noise at idle
I do have an unsteady idle before the engine warms up - car seems to have normal power it is not running hot.
One time I had cats go bad it was on my mustang - no power, engine ran HOT
I had the cats go bad on my land rover but that they were just falling apart on the inside made noise at idle
Any thoughts here - Car has 103,000 miles and is tracked once in a while - do the cats rattle on Boxsters?
Not sure about the uneven idle but years ago, I noticed a different smell after driving and found two of my axle boots cracked and flinging grease everywhere, including the exhaust.
No cats do not rattle, if they do you got chucks of the material inside degrading. Maybe your smelling leaking fluid dripping on to the exhaust or hot surface? Check fluid levels regularly.
+1 to grease from an axle boot burning on the exhaust. Look for dark residue on the exhaust where the axle crosses. A possible leak that would not have the classic 'burning oil smell' would be fluid coming from the power steering reservoir or overflow tube.
While the cats themselves do not rattle I have seen the heat shields come loose and rattle.
It's more frequent for a cat to plug and do what it did on your mustang than it is to see one fall apart from the inside like your rover.
Your smell may be a small oil leak (spark plug tubes are common culprit, drip into exhaust piping).
What does the noise sound like? A rear end rattle could be a lot of things.
I'd get the car up on jacks and have a look around to figure those two things out.
A fluctuating idle can mean a lot of things. If it's only with cold startup at idle, it's likely a small vac leak. Do a manifold vac test and see what that shows you.
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