20 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHOil Cap and Idle
Leading reported evidence
Check oil this morning and added a little
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
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 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.
Leading evidence: 'Check oil this morning and added a little' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check oil cap only' (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.
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
After I installed the new one, the idle barely changed with the oil cap off.
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
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 stopped and check my oil cap only to find it wasn't reinstalled properly .
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
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.
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
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
I pulled my TB off it was clean no residue clean , pulled the ICV same thing.
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
I had the local stealership tell me that the vacuum from a dead AOS would lead to RMS weepage, so they 'recommended' me doing the RMS at the same time..
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.
20 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.
Thought this experience may help someone else.
I checked my oil this morning and added a little. I quickly put my oil cap back on and started her up. She idled rough at 1st, then all was well until I came to a stop light. I noticed she was idling around 1500 rpms. It did this every time I came to a stop but ran fine.
I stopped and check my oil cap only to find it wasn't reinstalled properly . I put it back on, making sure it was snug and presto! The idle problem solved! I was surprised that just not having the oil cap properly snugged could cause this much of and issue, but it did.
Maybe this will help someone else diagnose an idle problem.
Manual states engine hot, off for several minutes, level ground. No ral difference between engine cold or hot, in my experience, so long as the oil is fully drained back.
I always check mine in the morning. I just make sure that the level guage says that the oil in over the mid-point. I've corrolated this with the dipstick and feel it gives a more accurate reading than when I fill up as that always a little on the low side. i believe that's because the oil hasn't draind back in the engine. If I stop the car for 5 minutes and don't fill up with gas, the oil guage reader will say I need to wait anywhere from 5-10 minutes before checking. I don't see why filling with gas changes that time. Plus I know my garage is level. I don't know about the gas station.
I hate to be the bearer of bad news but your Air Oil Separator is busted. Search for threads talking about the AOS, runs about $125 or so for the part alone.
If your oil seperator system is leaking, you would have no vacuum from the oil filler tube amd therefore, no idle change when cap is removed. Therefore, you can safely assume that you seperator is fine.
So to clarify on AOS, if you have a bad AOS you would not experience any idle change if the oil filler cap is remove while the engine is running.
Big buff of blue/white smoke when first start engine after hard driving point to bad AOS!
glad you caught that the oil cap was loose and put it back on. I let mine go long enough to get a check engine light on for idle out of range. Saved you a couple of bucks.
If the bellow is leaking, yes, the oil cap removal will not affect idle. If the vacuum lines that run to it are leaking, yes the oil cap removal will not affect idle.
If the diaphram is ruptured inside the AOS, removing the oil cap WILL affect idle.
Tippy
I hope you're wrong. Since it's been running fine and it seems to be a cause/effect type thing maybe I'll be lucky.
It ran fine last night. I put oil cap on wrong today and it idled high. I reinstalled oil cap with engine running, and it immediately corrected itself.
Anyway, reading about replacing an AOS on a 996, it doesn't sound like a fun DYI
Pat - the idle difference in mine was extremely noticeable and it would die within about 2 seconds when removing the oil cap. After I installed the new one, the idle barely changed with the oil cap off. There was a slight, I mean very slight vacuum when you cupped your hand over the filler neck. Before, with the ruptured one, it felt like it would suck your hand into the filler neck.
Slight vauum draw with little idle change (maybe ~50-100 RPM) is normal, drastic idle change with large draw, AOS is more than likely is dead
. GL
You are correct. With a properly working system, there really should be no measurable vacuum in the crankcase. The idle may or may not change very slightly and will eventually balance out (usually higher) when you remove the oil cap. The cooler the ambient temperature is, the more idle change you may experience. For those who have a vacuum level that can actuallly be felt when removing the oil cap....you have a problem and are probably using alot of oil. There is also a problem if your car stalls when removing the cap.
I had the local stealership tell me that the vacuum from a dead AOS would lead to RMS weepage, so they 'recommended' me doing the RMS at the same time..
No **** for the extra $1000 - what a croc.
Thoughts on the following please. 1999 cable car. The cars idle is normal, however stalls when you brake, push in the clutch come to a light the rpms fall normally but drop to the point of stalling. Always starts right back up no issues. If I remove the oil er cap my idle increases to about 800 at idle never stalls runs normally idles constantly smooth up or down. Car once shut off hot or cold takes 3 tries before it will start with cap off. No smoke ever no codes or check engine lights. Also I have vacuum/ suction with cap off on . I pulled my TB off it was clean no residue clean , pulled the ICV same thing. I believe I have more of a vacuum issue than Aos but not sure. Im also havent seen any difference in oil levles, conditiin quality, and zero smoke any time with or without cap . Thoughts or what to look at first is much appreciated thank you
This is a source reference. Confirm exact model applicability in the original material.
