12 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
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YOUR RESEARCHP0491 - Seek advice
Reported repair
Combined work: Replace vacuum hoses + Run so i knew it wasn't
Reported resolution
1
Reported fixes
0
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 report a fix
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.
Reported fix
I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that. Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL
Leading evidence: 'Combined work: Replace vacuum hoses + Run so i knew it wasn't' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'pump' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Combined work: Replace vacuum hoses + Run so i knew it wasn't' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Combined work: Replace vacuum hoses + Run so i knew it wasn't', supported by resolution reports in 1 discussions. 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
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.
Performed · outcome unconfirmed
Same thing happened on my Mercedes....replaced crack vacuum hose in that case.
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
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.
Performed · outcome unconfirmed
Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL
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
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.
Performed · outcome unconfirmed
I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that.
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
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.
Suspected cause · Original poster
He thought it was the pump, but since the car ran fine and we have no DMV pollution checks to worry about, he thought it would be fine to just let it go for the time being.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Combined work: Replace vacuum hoses + Run so i knew it wasn't
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
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.
Reported fix
I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that. Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
pump
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
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.
Suspected cause · Original poster
He thought it was the pump, but since the car ran fine and we have no DMV pollution checks to worry about, he thought it would be fine to just let it go for the time being.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Combined work: Replace vacuum hoses + Run so i knew it wasn't
1
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Discussions that report a fix
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.
Reported fix
I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that. Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL
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.
12 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 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: 20261027T031046Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
'02 C2, 176,000 miles, original engine. Owned 7 years.
About 2 years ago my car started throwing code 0491 (secondary air injection system, IIRC). Had my P car Indy look at it when I had it in for something else. He thought it was the pump, but since the car ran fine and we have no DMV pollution checks to worry about, he thought it would be fine to just let it go for the time being.
It would throw the code occasionally, although under all kinds of circumstances, so I couldn't draw any conclusions. Lately it's happening more often. Car runs flawlessly. Do I need to address this?
I had the same problem on my boxster....I thought it was the pump but I tested it using my durametric and it ran so I knew it wasn't that. Ended up being the vacuum lines...cracks in the rubber fittings....replaced them and all good....no more CEL
Won't hurt car other than maybe foul cats is what I heard since fuel will be too rich. Air injection pump just makes sure there is more oxygen in the exhaust so that unburned fuel will burn in the cats....at least that what I have been told.
Bill, the air injection does not effect the engine....in the first 30sec when the air pump turns on and the engine is cold, engine tends to run rich whether pump is on or not. The injection happens in the exhaust system and not the engine so there is no impact to engine combustion whether the injection works or not. This is purely an emissions thing to burn off gasoline vapors in the cats.
Southern man, the vacuum lines are needed to open up valves to exhaust system so air can be pumped in. Once engine is warm pump turns off and valve closes so exhaust won't backflow into pump and foul it.
Same thing happened on my Mercedes....replaced crack vacuum hose in that case.
Report back on what eventually solves your CEL
Lol, I shouldn't get on the forum at 3am before having my coffee!
Now help me understand this, if the SAI vacuum leak gives a false reading, then adding more fuel, does it not wash down the cylinder?
I got the same CEL after i accidentally smashed a vacuum hose taking my alternator out. All of the plastic gets brittle with age and its easy to crack a line. Good luck, hopefully the crack is easy to spot
Think of it this way....the combustion has already happened...the exhaust leaves the engine with still some unburnt fuel vapors mixed in....it goes to the catalytic converter which are not hot enough so all the vapors don't burn yet because there isn't enough oxygen....so they inject oxygen before the cats so it could burn more fuel and get cats hotter faster so they are full function sooner and lower emissions. Air injection pump is all about cat efficiency and has nothing to do with engine other land the oxysensors detect the problem and CEL. I am no expert but I am pretty sure I have this right....so stop worrying about fuel wash
Understood. I haven't done much research on the SAI and how it functions.
Isn't the air injected through the intake runne
r?I now see it feeds into the head. I had this visioned all wrong...More, coffee and reading needed!
I appreciate the quick 101.
