Irratic Idle After Hard Driving!
05-05-2011, 05:46 AM
#1
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Irratic Idle After Hard Driving!
Hi guys,
I realised that after some hard street driving, when i reach home and park my porky, the idling would get all irratic. It would drop to about 500rpm for a second and then move back up to 800rpm and idle in the range from 600rpm to 800rpm and at times drop to 500rpm .... Ideas?
Cheers
I realised that after some hard street driving, when i reach home and park my porky, the idling would get all irratic. It would drop to about 500rpm for a second and then move back up to 800rpm and idle in the range from 600rpm to 800rpm and at times drop to 500rpm .... Ideas?
Cheers
05-05-2011, 03:04 PM
#4
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Hi guys,
I realised that after some hard street driving, when i reach home and park my porky, the idling would get all irratic. It would drop to about 500rpm for a second and then move back up to 800rpm and idle in the range from 600rpm to 800rpm and at times drop to 500rpm .... Ideas?
Cheers
I realised that after some hard street driving, when i reach home and park my porky, the idling would get all irratic. It would drop to about 500rpm for a second and then move back up to 800rpm and idle in the range from 600rpm to 800rpm and at times drop to 500rpm .... Ideas?
Cheers
And no check engine light.
Another time, much more recent, the idle started doing swinging again, and this time severe enough on the low side I thought the engine was going to stall, and the cause turned out to be a bad passenger side VarioCam solenoid and VarioCam actuator. But in this case the CEL came on and an error code was logged that pointed to the VarioCam system. Maybe P1539 (Camshaft adjustment bank #2).
Sincerely,
Macster.
05-05-2011, 03:19 PM
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My 02 Boxster suffered a similar symptom as the original AOS was going bad. A hunting idle was one of the first symptoms, though this was a long time ago and my memory is fuzzy but I don't recall the idle swings that severe.
And no check engine light.
Another time, much more recent, the idle started doing swinging again, and this time severe enough on the low side I thought the engine was going to stall, and the cause turned out to be a bad passenger side VarioCam solenoid and VarioCam actuator. But in this case the CEL came on and an error code was logged that pointed to the VarioCam system. Maybe P1539 (Camshaft adjustment bank #2).
Sincerely,
Macster.
And no check engine light.
Another time, much more recent, the idle started doing swinging again, and this time severe enough on the low side I thought the engine was going to stall, and the cause turned out to be a bad passenger side VarioCam solenoid and VarioCam actuator. But in this case the CEL came on and an error code was logged that pointed to the VarioCam system. Maybe P1539 (Camshaft adjustment bank #2).
Sincerely,
Macster.
05-05-2011, 03:50 PM
#6
Race Director
A dirty/malfunctioning idle control valve can result in an erratic idle.
For a suspected AOS there are a couple of things you can do to possibly confirm that the symptom is from a failing AOS.
One is to with the engine idling unscrew and remove the oil filler tube cap. Sometimes a failing AOS causes such a huge pressure difference in the engine crankcase compared to outside of the engine crankcase the cap is nearly impossible to impossible to remove.
However, if you can remove it with ease this is not 100% proof the problem is not the AOS. Either AOSs can fail in one of several ways and some of the symptoms vary or the AOS manifests different symptoms as it goes from slightly feverish to just before it reaches death's door. I sort of favor the latter since I cut open one bad AOS and there ain't that much to go wrong inside of one. I found a crack from I suspect material fatigue in the rubber/cloth reinforced diaphram. My belief is as this crack or initially a pinhole grows in size the symptoms transistion.
Anyhow, another check you can perform on your way to confirming or eliminating the AOS is to check the throttle body for presence of oil. To do this you'll have to remove the TB.
The AOS connects to the manifold at a connector behind (downstream) of the TB (at least on my Boxster but I think the layout's similar for the 996 engine) and a failing AOS can pass a lot of oily vapor into the intake.
Due to the proximity of the TB to this connector the TB can become rather oily.
If you find this condition, again this points to the AOS but does not rule out another cause for the engine's behavior.
Sincerely,
Macster.
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05-05-2011, 11:40 PM
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What is the make/model and year of your car and what's the mileage? IIRC early 996 models (equipped with the 3.4l engine?) came with an idle control valve. Later models fitted with e-Gas do not have an idle control valve.
A dirty/malfunctioning idle control valve can result in an erratic idle.
For a suspected AOS there are a couple of things you can do to possibly confirm that the symptom is from a failing AOS.
One is to with the engine idling unscrew and remove the oil filler tube cap. Sometimes a failing AOS causes such a huge pressure difference in the engine crankcase compared to outside of the engine crankcase the cap is nearly impossible to impossible to remove.
However, if you can remove it with ease this is not 100% proof the problem is not the AOS. Either AOSs can fail in one of several ways and some of the symptoms vary or the AOS manifests different symptoms as it goes from slightly feverish to just before it reaches death's door. I sort of favor the latter since I cut open one bad AOS and there ain't that much to go wrong inside of one. I found a crack from I suspect material fatigue in the rubber/cloth reinforced diaphram. My belief is as this crack or initially a pinhole grows in size the symptoms transistion.
Anyhow, another check you can perform on your way to confirming or eliminating the AOS is to check the throttle body for presence of oil. To do this you'll have to remove the TB.
The AOS connects to the manifold at a connector behind (downstream) of the TB (at least on my Boxster but I think the layout's similar for the 996 engine) and a failing AOS can pass a lot of oily vapor into the intake.
Due to the proximity of the TB to this connector the TB can become rather oily.
If you find this condition, again this points to the AOS but does not rule out another cause for the engine's behavior.
Sincerely,
Macster.
A dirty/malfunctioning idle control valve can result in an erratic idle.
For a suspected AOS there are a couple of things you can do to possibly confirm that the symptom is from a failing AOS.
One is to with the engine idling unscrew and remove the oil filler tube cap. Sometimes a failing AOS causes such a huge pressure difference in the engine crankcase compared to outside of the engine crankcase the cap is nearly impossible to impossible to remove.
However, if you can remove it with ease this is not 100% proof the problem is not the AOS. Either AOSs can fail in one of several ways and some of the symptoms vary or the AOS manifests different symptoms as it goes from slightly feverish to just before it reaches death's door. I sort of favor the latter since I cut open one bad AOS and there ain't that much to go wrong inside of one. I found a crack from I suspect material fatigue in the rubber/cloth reinforced diaphram. My belief is as this crack or initially a pinhole grows in size the symptoms transistion.
Anyhow, another check you can perform on your way to confirming or eliminating the AOS is to check the throttle body for presence of oil. To do this you'll have to remove the TB.
The AOS connects to the manifold at a connector behind (downstream) of the TB (at least on my Boxster but I think the layout's similar for the 996 engine) and a failing AOS can pass a lot of oily vapor into the intake.
Due to the proximity of the TB to this connector the TB can become rather oily.
If you find this condition, again this points to the AOS but does not rule out another cause for the engine's behavior.
Sincerely,
Macster.
