21 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH'99 996 Idle Issues
Reported repair
Clean maf repeatedly
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
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Reported fix
And another thing to add: I cannot remember my exact symptoms (sorry), cleaned MAF repeatedly, then figured WTH and bought a new Porsche MAF. That fixed it.
Leading evidence: 'Clean maf repeatedly' (1 discussions report resolution; 0 report an unsuccessful attempt). Across 1 matching discussions, the most frequently mentioned possible cause is 'air oil separator' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Clean maf repeatedly' (1 discussions). For that action, 1 discussions report a resolution and 0 report an unsuccessful attempt. The most frequently reported fix is 'Clean maf repeatedly', 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.
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Reported cause
That idle behavior from my Boxster proved to be an AOS.
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.
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Reported cause
Mine with similar symptoms turned out to be intake boots, my car is higher mileage, 125k
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.
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Performed · outcome unconfirmed
Replaced the idle control valve, throttle position sensor, cleaned throttle body.
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Performed · outcome unconfirmed
I cleaned the throttle body and the engine perked up some but the improvement was short lived.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Clean maf repeatedly
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
And another thing to add: I cannot remember my exact symptoms (sorry), cleaned MAF repeatedly, then figured WTH and bought a new Porsche MAF. That fixed it.
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
Clean maf repeatedly
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
And another thing to add: I cannot remember my exact symptoms (sorry), cleaned MAF repeatedly, then figured WTH and bought a new Porsche MAF. That fixed it.
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.
21 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.
1 acknowledgements have no verified action link; they do not establish a repair result.
Hi,
I am having intermittent idle issues on my 1999 996 3.4 with 88,xxx miles. Sometimes the car runs fine and normal, but sometimes with the AC on it idles steadily at anywhere 1200-1600 rpms and with the AC off surges between 500 and 800 rpms. Any ideas what can cause this? I plan on disconnecting the battery for a while to reset the ecu, and removing and cleaning the MAF sensor tonight, so that might possibly fix it. Any input is appreciated.
If it's cabled throttle, it's good to clean the idle control valve as well. Need to remove it and power it with a 9v battery and spray with carb cleaner.
Two weeks ago I ordered a new idle control valve, installed it, cleaned the throttle body, and the MAF sensor. The car ran like brand new for two weeks. This morning it started acting up and is back to its old ways. Any ideas?
That idle behavior from my Boxster proved to be an AOS.
You can try the remove the oil filler tube cap "test" with the engine idling.
However, the AOS, if it is the AOS, may not be far enough gone to produce excessive vacuum though, so if the cap comes off with no real struggle that does not let the AOS off the hook. Once the cap removed the engine will react. That is normal, as the removal of the cap creates a big intake air leak. Put the cap back on and the engine should recover in practically no time.
When investigating the cause of the symptoms I found the area right behind the throttle body very oily, the area where the hose from the AOS connected to the intake manifold. Also, the throttle body was oily, especially the butterfly valve. It was wet with oil. Well a drop was hanging at the bottom of it.
The significance of the presence of oil didn't dawn on me until later. I cleaned the throttle body and the engine perked up some but the improvement was short lived.
Did you clean it out with MAF cleaner? And did you clean up the Idle Control Valve and Throttle Body? Before buying a new MAF sensor, clean it. Did you reset the ECU by disconnecting the battery because it was throwing a CEL? Would help to know if you are getting any codes. Just so you know, the MAF sensor does not have much to do with idle and low RPM's. If I remember correctly it starts to come into play at about 1400 rpm. However a fouled one might be sending the DME incorrect information.
Other sources of idle surge have been mentioned. Try removing the oil filler cap while the engine is running as stated and see what happens. Vacuum leaks are a common factor with idle and surging. Places to check, oil filler tube cracks, AOS, vacuum hoses and vacuum canister, intake clamps on TB and plenums for starters.
Now I see. Like Ahsai asked...is the new ICV original Porsche? After that, leaning towards a vacuum leak. Any CEL codes? And another thing to add: I cannot remember my exact symptoms (sorry), cleaned MAF repeatedly, then figured WTH and bought a new Porsche MAF. That fixed it.
cleared the codes p0102 and p0112 from the MAF being unplugged. Car ran fine all weekend, then Monday morning started acting up again. Im going to rule out AOS temporarily because 1. the car does not die when you remove the oil cap, however the revs do drop, 2. if you put your hand over the oil filler tube with the engine running the suction feels the same as on my buddys 911 that is running well. I ordered a Bosch MAF sensor off amazon last night and it should be here tomorrow.
Time to start taking a close look at all of those vacuum lines. Maybe a smoke test if you have access to a smoke tester (or a cigar - see YouTube for ghetto smoke test instructions)...
Honestly, I found it easier to just replace all the vacuum lines rather than trying to find the leak.
Here are a few good threads:
http://www.renntech.org/forums/topic...-vacuum-lines/
https://rennlist.com/forums/996-foru...m-diagram.html
http://www.renntech.org/forums/topic...-out-of-ideas/
http://www.bimmerfest.com/forums/sho....php?p=4519113
Did you ever figure out what your idle issue was caused by?
I know this thread is over a year old, but I have exactly going on with my car as what you were experiencing. I did most of what you did, cleaning things, replacing things, oil cap removal and so forth....
I'm leaning towards a failing AOS at this point...
interested to see what your fix was if that's the case...
Knocking on wood as I type this, but one day it just quit doing it. I have put another 8000 miles on the car with no issues. Only advice I have for you is to order parts on Amazon, if they don't fix your problem, you can take them off and send them back for a full refund.
Hey, thanks.
Your entire story reads just as mine to the T.
Replaced the idle control valve, throttle position sensor, cleaned throttle body. Smoke tested for vacuum leaks, etc. Nothing seems to fix it.
When I remove the oil cap there is no idle change which I'm told is good. No excessive vacuum when I remove it which I'm told is good. Both indicate AOS is ok. No smoke from tail pipes.
Some times my idle runs high and other times I get the hunting idle bouncing from around 500 & 800 rpm. Both can occur when engine hot or cold. And to boot, it can idle great for weeks then out of the blue idle bad at a stop light, then next light it's fine.
Only thing I have not done is replace the oil filler tube cap. It seems tight but the rubber gasket is chewed up a bit but looks like it should seal properly.
When I do notice the idle problem and pull over and take off the oil filler cap and then replace it the idle corrects.
Thanks for updating me. I put in all the details in case someone else wants to chime in with their thoughts.
Just changed my oil tonight.
I had noticed my oil level was high, about 2mm over the little dot on the dip stick.
I was thinking maybe my idle problems were related to too much oil, is this possible or not?
Took it out for a good 80-90 miles drive with many stops, and it never once idled bad, in fact it seemed to idle spot on. It's been idling bad at least 2 or 3 times every time I've driven it for the last few months or longer.
Maybe I'm on to something here.
Maybe that's why yours corrected itself jrp3000, maybe you changed the oil and that's when yours stopped.
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