4 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHVapor lock?
Reported or suspected cause
idle air control valve
Reported cause
No successful repair reported for this finding.
1
Identified cause
0
Suspected cause
0
Reported fixes
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 identifying a cause
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Reported cause
Another likely culprit is the idle air control valve.
Leading evidence: 'idle air control valve' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'idle air control valve' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Check manually' (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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Discussions that performed work without a confirmed outcome
1
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Performed · outcome unconfirmed
Can be removed and cleaned with carb cleaner, or simply replaced.
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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Suggestion
Not sure if the car monitors fuel pressure, but if not, put a gauge on it, and check manually.
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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Suggestion
I would add to what 5CHN3LL had to say by offering be sure to check the oil filler tube cap for a leak.
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.
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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.
4 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: 20261027T154520Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
My 99 cabrio has a tough time at stop lights. It's been going on since last summer but stopped during the winter months. At a stop light the car will stall out if I don't keep my foot on the gas pedal goosing it slightly and at low speeds it will sputter ever so lightly. I've had the fuel pump replaced, the fuel filter and most recently the idle air control valve. Two authorized dealers are scratching their heads over it although one is now thinking it might be the evap valve sticking. There are no codes pointing in any direction.
Has anyone experienced this and if so what was your solution?
Thanks guys.
Have they done a smoke test for a vacuum leak? A vac leak at idle will cause exactly that symptom. A cracked oil filler tube is one of many possible culprits for a vacuum leak.
Try unplugging the MAF sensor (the sensor between the airbox and the throttle body). If the rough idle clears up, the MAF sensor may be bad.
I would add to what 5CHN3LL had to say by offering be sure to check the oil filler tube cap for a leak.
My experience is this can leak and affect the engine at idle. It does so because while the leak is small the amount of air that is admitted by the leak represents a good portion of the total amount of air the engine is using at idle. But above idle the amount of air the leaking cap passes represents just a small amount of the total amount of air the engine is using and has minimal impact.
With the engine up to temperature and idling -- if it will idle -- see if you can move the cap about and if the engine reacts. In my Boxster's case I was able to pull up on the cap and cause a leak and even when I released the cap it stayed up and the leak remained. This was even though the cap was properly secured. My WAG is the cap's o-ring shrinks or suffers some wear over time/miles.
In my car's case I found the cap lasts around 150K miles, but always of course, YMMV. My car with just over 301K miles in on its *2nd* oil filler tube cap.
Also, doesn't the '99 MY engine have an ICV (idle control valve)? If so this can be suspect. There are DIY articles on testing this, cleaning it, even replacing it, if (big if) the ICV is the correct diagnosis.
Unlikely a vapor lock issue, but remotely possible.
Failing fuel pump comes to mind. If it does it only in summer, the fuel chemistry changes. Along with added ethanol to fuel, it all plays havoc with fuel pumps. Not sure if the car monitors fuel pressure, but if not, put a gauge on it, and check manually.
Another likely culprit is the idle air control valve. In summer, they can get stuck due to heat soak. Can be removed and cleaned with carb cleaner, or simply replaced.
This is a source reference. Confirm exact model applicability in the original material.
