2004 c4s smoking badly

Guys, I am still in search of different things to look at on my 2004 c4s but figured I would post up what's happened over the last couple days and see if anyone has any ideas before I just keep trying random things (also tied up for the next few days so not sure when I will get a chance to really dig into it).. Yesterday I was driving around as my mom and dad flew in for a few days.. Everything was driving great. Turned in to get gas and ran over a bunch of lose gravel (nothing too bad).. Ran into Costco and when I came back I noticed a loud squeal from the engine as soon as I started it up (went away above 2k rpm).. I figured a belt.. Went and filled up with gas and then car didn't start very well (had to give it a bit of gas to get it running.. Once running it idled fine but still squealed).. Drove home (about 10kms) and no issues except for a squealing belt when below 2k rpm.. Came home called napa and ordered a new belt. Took the airbox out and popped the belt off for inspection. I noticed a lot of small little pebbles that were in the groves of the belt (had to pry them out with a screw driver). Once I picked out all the pebbles I checked all tensioners and pullies and didn't see any issue.. I decided to start the car to inspect the belt with engine running (I left the airbox out and map/maf unplugged) got a couple errors for pasm and abs (this is when I realized I left the map sensor unplugged).. Put everything back together and took it out for a 5km drive to make sure everything was good and the squealing was gone.. All was good. Now on to this morning. My dad wanted to checkout a car about 70kms away so we took the Porsche.. I notice while getting on the highway there was a lot of white smoke so I pulled over (also saw a cel). Checked the code on the side of the highway and it was p0507 was my scanner called idle control system rpm higher than expected. I thought maybe I didn't have the connection on the map on correctly so I popped it off and reinstalled.. Started up and got back on the highway and there was some smoke as I got up to speed but once at speed everything was fine. I got off the highway and once in town most times I would take off I would see a bunch of smoke. I took the car back home and we took my truck out to look at the car and pickup a new belt. I got back and threw the belt out and started the car. At startup there was a lot of smoke. Drove just up the road and still lots of smoke under acceleration (not even hard acceleration). With little/no throttle there is no smoke (except on startup last time). The oil level (electronic) said I was low in oil so I threw in 1/2 quart (will go out and recheck oil level manually). Not sure if you guys have any ideas? The smoke is very white and car idle isn't too bad but isnt solid. When engine is warmed up it goes from 650rpm-800rpm.. Thanks guys

Not a good story! I think the belt etc is coincidental but its sounds like you air oil separator (AOS) is dead or dying. White smoke is burning oil, the engine guru's will chime in soon i'm sure.

​​​​​​high vaccuum at oil filler tube with cap off? Greasy/oily throttle body butterfly valve and intake further beyond? Most probably AOS on its way out

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What Silk said and I would also check the water pump and the coolant tank. White smoke could be coolant. Belt drives water pump so many that's related.

Assuming smoke is coming out of tailpipes, my vote would be AOS. Get a spare oil fill cap modify so a small hose can be attached to a manometer gauge. Test vacuum. Should be 3" to 5"(if my memory serves me correctly) at warm idle. Failing AOS will be higher. Much better test than pulling the cap by hand as my arm is not calibrated for differences in vacuum and idle will change even if AOS is good due to this creates a large vacuum leak!

I've also heard that taking off the oil filler cap while the car is idling is a quick and dirty test for the AOS. The engine should continue to run with the cap off - if it stalls it indicates an issue.

I would also check oil pressure....I had similar symptoms on the track and everyone was pretty convinced it was AOS....engine ran with cap off. went back out and 5 laps later my engine grenaded. It ended up being oil starvation and crank bearing failed.

The squeal and white smoke is almost definitely the AOS. I had the same symptoms on my Boxster. Had to take apart the throttle body and clean it all out. Was a PIA to replace but runs much better now. I built a simple H20 slack tube manometer using an old oil cap to test with plumbing parts from the local hardware store as I couldn't find a vaccum gauge that read that low accurately. For the Boxster it should read between 4 and 7 inches of water. If you try and take off the oil filler cap it should be hard to remove due to the extreme vaccum in the crankcase. I am less sure on the 911 as the design is slightly different but you can on the Boxster short term disconnect the return tube to the throttle body and plug it up on both the tube end and the throttle body end to reduce the oil contamination.

Sure sounds like an AOS failure !! I have seen a couple failed AOS's that also caused a squeal of the RMS due to the high crankcase vacuum !! One had came in from an Indie who had failed to repair the squealing sound coming from the clutch/flywheel area under 2000 rpm (they had replaced the clutch, flywheel, T/O bearing). The cause of the squeal was the RMS due to a failing AOS. Test the crankcase vacuum using a gauge calibrated in in/h20 ( inches of water). 4-7 in/h20 https://www.zoro.com/zoro-select-pre...99/i/G4738824/ https://www.ebay.com/itm/Marsh-gauge...UAAOSw2gxYuHX1

Going to order the aos and a spare oil cap and manometer.. Is there anything else I should replace while in there for the aos? Just don't want to go through all the work of that if there's a few small other things that should be done while I'm in there..dealer said a week for the parts so most likely I'll just order online.. Just want to make sure I get everything I need

The plastic hoses to the AOS will be brittle. Replace those, too. Also plan on replacing the AOS water line fitting to the right of the alternator with the metal replacement, or one you can fashion yourself from a brass barb fitting. GLWR.

Will look into the part numbers and get these ordered tomorrow.. Car is up on the lift ready to go when the parts get here but being in Canada I expect about a week to get the parts.. Thanks to everyone for confirming my original suspicion (I am almost certain that's the issue but will order an extra oil cap and vacuum gauge to verify prior to ripping everything out).. Also lopue : I'm always keeping an eye on oil pressure and all the temps but after hearing th e squealing and replacing the belt I've had an eagle eye on everything and it all seems normal.. Good advice tho.. Sad I won't be able to drive it but gonna take the Italian one out for a bit (have a Lamborghini arranged race school scheduled for next weekend and completely stoked about it)..

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I think my oil cooler o-rings were replaced when my AOS was done.