Solution Update - my problem ended up being caused by a faulty oil filler cap that was just loose enough to cause a significant vacuum leak to the point that the car barely ran\idled.


Symptoms:
- Idle surge to 3000 rpm on startup

- Final idle after about 90 seconds was so low and unstable the car barley stayed running
- - Initially I had NO CODES - it was a mystery - -

- Finally after much trial and error I got multiple misfire codes and the car started to run and smell terribly rich - which really pointed at a vacuum leak








Morning Xoutpost - I've got a strange one that I can't seem to track down, it's persistent and doesn't seem to throw codes - which is driving me insane.


Ok, the issue: - On ANY START, not cold, not hot, any start, the car will start fine, immediately "spike" up to 3000 RPM and then drop to just under 1000 RPM over about 3 seconds and then about 90 seconds after that it drops to about 700 RPM. All of this is normal for the car except the jump to 3000 RPM part, it used to just start, grab idle and hang at about 1000 RPM for 90 seconds until it warmed up and dropped to 700.



It's what happens after that, that is the bigger issue. Once low idle sets in the RPM will slowly over about 15 seconds climb to 1000 RPM and then drop to almost stall, level off for maybe 30 seconds (though it's still a bit rough), climb to 2000 RPM and then act like it wants to stall again.


This cycle will repeat itself over and over, the car won't stall but it won't idle either - and if you just put it in gear and drive away - it seems to run fine - not down on power, doesn't lag, doesn't fall on its face, miss or other, seems to run fine -> but won't idle.


So far I have:
- Changed the oil, just for giggles sake
- Pulled and re-seated the vanos solenoids & solenoid plugs

- SUPER cleaned the MAF and Throttle Body (with MAF cleaner specifically)

- And ran a hand along all of my vacuum lines, ports and plugs
- Swapped cam position sensors to try and isolate it to a sensor or bank
- Checked and cleaned the CCVs (lines and diaphragms)



And nothing made even the slightest difference?? At the moment, I'm stumped...



Thoughts?