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99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

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3 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCH99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Reported or suspected cause

idle air control valve not actually opening

Suggestion or failed attempt

No successful repair reported for this finding.

0
Identified cause: 1
Suspected cause: 0
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: 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
I believe the issue is with the idle air control valve not actually opening when it should be.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Frequently discussed work

Replace air / fuel ratio, and cause a

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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 · Original poster
I somewhat expected that if the IACV valve opened during the testing, that it would change the air / fuel ratio, and cause a change in RPM, but that did not happen.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

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Leading evidence: 'idle air control valve not actually opening' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'idle air control valve not actually opening' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Replace air / fuel ratio, and cause a' (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.

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1 matching discussions · 3 captured posts examined · 0 partial discussions

Compare 3 other evidence results

Replace air / fuel ratio, and cause a

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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 · Original poster
I somewhat expected that if the IACV valve opened during the testing, that it would change the air / fuel ratio, and cause a change in RPM, but that did not happen.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Replace bosch

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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
Just order a generic to replace the Bosch, so we’ll see if my results are fully identical to yours.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Run poorly

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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 · Original poster
My understanding is that if the ECM believes the IAC to be open and allowing additional air into the engine, but it actually is not, that would result in the air / fuel ratio to be too rich with fuel, which would explain how the engine is running poorly.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Frequently discussed actions (3)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Replace air / fuel ratio, and cause a

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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 · Original poster
I somewhat expected that if the IACV valve opened during the testing, that it would change the air / fuel ratio, and cause a change in RPM, but that did not happen.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Replace bosch

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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
Just order a generic to replace the Bosch, so we’ll see if my results are fully identical to yours.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Run poorly

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
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 · Original poster
My understanding is that if the ECM believes the IAC to be open and allowing additional air into the engine, but it actually is not, that would result in the air / fuel ratio to be too rich with fuel, which would explain how the engine is running poorly.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Reported and suspected causes (1)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

idle air control valve not actually opening

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
I believe the issue is with the idle air control valve not actually opening when it should be.
Original post Read captured discussion
99 986 - idle air control valve buzzes but does not open - 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.

3 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: 20261027T173940Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1 / ORIGINAL POSTEROriginal post

I am having an issue with my 986 2.5 running rough, seemingly to be very rich when below 2500 rpm or so. I believe the issue is with the idle air control valve not actually opening when it should be. My understanding is that if the ECM believes the IAC to be open and allowing additional air into the engine, but it actually is not, that would result in the air / fuel ratio to be too rich with fuel, which would explain how the engine is running poorly. Twice now I have bought a new (although generic) IACV. My original (bosch), and the 2 new generic ones all do the same thing. They buzz loudly when the key is in the ACC position, but the engine is not running. I tried testing them with the durametric test, and they buzz very loudly, and then buzz quieter, back and forth every few seconds. I tried performing that test both while the engine was idling, and the idle speed did not change as the test was running. I somewhat expected that if the IACV valve opened during the testing, that it would change the air / fuel ratio, and cause a change in RPM, but that did not happen. IACV video of it buzzing with key in ACC position, but not opening: https://streamable.com/3jwhgn IACV video of the sounds it makes when having my durametric perform the IACV test: https://streamable.com/mv6a1l It seems highly unlikely that I would have 3 bad IACV valves, so I am leaning towards the ECM sending a bad signal to them somehow. Anyone have any idea where to go from here? Much thanks.

POST 2Original post

Hello - Did you happen to find the cause or a solution? I just rebuilt my engine and I have the same issue. Just order a generic to replace the Bosch, so we’ll see if my results are fully identical to yours.

POST 3Original post

Confirmed that the generic buzzes exactly the same.

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