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If the oil cap is hard to remove, you have a high vacuum level in the sump, which is bad for a variety of reasons, including lean stalling. The correct way to access the AOS is to fully warm up the engine by driving the car for 10-15 min, then replace the oil cap with the one in the picture above with a hose that connects to the digital manometer. If the vacuum level exceeds 6-7 inches of water vacuum, the AOS is leaking air into the intake system, causing the lean stall conditions. The normal level of vacuum is typically 4-5 inches of water, which is a really weak vacuum level, so it doesn't take much of a leak to cause problems, which is why we always checked every car that passed thru the shop with the manometer.

I asked my service advisor last night for specific measurements, but all I got back from him was "Oil cap hard to remove", which in all fairness is his level of mechanical expertise and understanding (he came from Porsche sales and doesn't know much about how the cars actually function in terms of problems, and the techs know this, but he does go out of his way not to sell unneeded work). I don't doubt the AOS is starting to fail after 14 years and around 150K miles (no visible symptoms yet), but more worried that replacing the AOS won't solve the cold start stalling problem (only stalls after initial cold start in the morning with the headlights on, but never after that). I'm going to the dealership to talk to the techs and get the details firsthand, and will report back what they say. And it's not like I don't spend enough at the dealer that they need to make more money off of me. I went deer hunting on a canyon road at 60 MPH, and instead of filing a comprehensive claim with my insurance for my '08 Cayenne, I'm having the dealer fix everything, including subletting all the body work.

The AOS can either be pin pointed or eliminated by having the car's sump vacuum level checked with a digital manometer (most quality shops have them as the AOS is a perpetual issue; surprise the dealer didn't do this).

See if any of the fault codes have changed. If not, then I would still go the path based on the FRAU readings.

Thanks Loren, as always! None of these are sounding like they are caused by the AOS going bad, are they? I'm going to visit the dealer to see what's going on tomorrow. From the way my wife has described the symptoms, it seems like it would be a fuel or electrical issue causing the car to sputter and/or die. The CEL didn't start until after the first visit where the tech cleaned the throttle body. Before that, it was idling smoothly, just stalling. I'll see if I can get more details. Anything else this could likely be?

P2189 Lambda control adaptation FRAU (lower load range) (FRAU > 0.7) - below limit value Possible fault causes - Incorrect main filling signal from hot-film mass air flow meter - Fuel pressure too high - Injection valve faulty (dripping) - Tank vent faulty (does not close completely) P2189 Lambda control adaptation FRAU (lower load range) (FRAU > 1.3) - above limit value Possible fault causes - Intake system leaking (secondary air) - Incorrect main filling signal from hot-film mass air flow meter - Leak in exhaust system - Fuel pressure too low - Fuel injector faulty (stuck) - Fuel pump delivery too low P2187 Lambda control adaptation FRAU (lower load range) (FRAU > 0.7) - below limit value Possible fault causes - Incorrect main filling signal from hot-film mass air flow meter - Fuel pressure too high - Injection valve faulty (dripping) - Tank vent faulty (does not close completely) P2187 Lambda control adaptation FRAU (lower load range) (FRAU > 1.3) - below limit value Possible fault causes - Intake system leaking (secondary air) - Incorrect main filling signal from hot-film mass air flow meter - Leak in exhaust system - Fuel pressure too low - Fuel injector faulty (stuck) - Fuel pump delivery too low

Original owner 2005 997 Carrera Tip, 191K miles, my wife's daily driver. Engine replaced by Porsche in 2011 around 60K miles when IMS bearing let loose. Lately in the morning on cold start, the car stalls at the end of the driveway first thing in the morning with the headlights on. Then runs OK, or sometimes stalls one more time in the next block. Doesn't stall when the headlights are on, but stumbles once or twice in the first few minutes of driving in the morning, then all is fine. Took to the dealer (never had any complaints), and the tech cleaned the throttle body. Check engine light came on by the time I got it home and the car continued to stall in the mornings. I'm in So Cal, so cold start is in the 50s outside temperature. Codes are P2189 and P2187, which indicates the engine's air-fuel mixture is too lean on bank 2 and bank 1 while idling. Tech then said found broken line for brake booster and replaced. Check engine light still on. Car still stalls. I then replaced the 9 year old Optima with a new AGM battery, but that didn't solve the problem. Back at the dealer this morning. Service advisor is now telling me the techs think it's a bad AOS, even though the car isn't smoking. Story is coming from 3 techs, including shop foreman. Their diagnosis was based on oil cap is hard to remove, and "oil filler neck is sucking in". I asked for what pressure measurement they got for crankcase vacuum, but didn't get a straight answer. Before I spend $4K to replace the AOS, which doesn't seem to me that it's the cause of the problem because there's no smoke on startup, what else should I have them look at?

Could be the harness, or just low voltage on the harness.

Thanks for the input. Dealer put in new plugs and swapped coils with no change. Saying the misfire count is very intermittent and that all coils are firing normally. Here is what they said "tested for misfires and monitored misfire count and found a small 1-3 count and multiple cylinders. Swapped coils and plugs for cyl 1,3,4 and found small misfire counts still present in same cylinders. Drove vehicle and found the misfire counts are very sporadic but will not re set the fault". Is it possible that the harness supplying power to coils could be the culprit? Just a random thought. Appreciate your help.

Plug or coil pack on cylinder 4.

Got the check engine light on my 24 718 GTS 4.0. Scan error code was P0304 and it was thought to be a fuel issue. Change of fuel did not solve so they changed spark plugs, no help. Error wont re set. Car is pretty new with <1600 miles. Anyone got any ideas?

P1276 Signal Delay Time for Oxygen Sensor Ageing, Bank 2 – Above/Below Limit Possible causes: – Oxygen sensor ahead of TWC – Leak ahead of TWC or in the area of the oxygen sensor after TWC – Wiring (oxygen sensors exchanged)

Hi all - getting my Boxster back on the road. Has been garaged on trickle charger for about 8 months. I've driven it the past couple of days with no issues, but today, I got a solid CEL (P1276 when I used my code reader). Below are the "live" values I was able to capture from the code reader. From what I read this points to 02 sensor. I have cat bypass pipes and aftermarket muffler on my boxster, but I have the stock headers (and don't remember ever messing with 02 sensors during the swap). To be honest, I dont know if this means I have 2 02 sensors or 4 on the stock headers. There's no 02 bungs or sensors on the cat pipes or muffler. Can yall tell me what best plan of attack is here? 2000MY non-S with roughly 95k miles and no other issues present. Param Value Bank1 Sens1 02S Outp 0.100V Bank1 Sens1 STFT 6.2% Bank1 Sens2 02S Outp 0.110V Bank1 Sens2 STFT 99.0% Bank2 Sens1 02S Outp 0.600V Bank2 Sens1 STFT 2.3% Bank2 Sens2 02S Outp 0.710V Bank2 Sens2 STFT 99.0% Engine RPM 828 Fuel System 1 Closed loop Fuel System 2 Closed loop Load Value: 3.50% LTFT Bank1 -13.20% LTFT Bank1 -11.70% STFT Bank1 5.40% STFT Bank2 6.20%

The frame does seal properly, but I think the outside (see picture from original post) of the frame is misshapen. Do you think heating the area with a heat gun and gently pulling the area would help bridge the gap?

Could be the fram or the window is warped. Does the frame seal properly around the door?

The larger (lighter) near object is a turbocharger - if there is oil coming out of that then you likely need a new one. I am not sure if anyone can rebuild them these days or not.

Hello all! I replaced my driver-side front window recently and replaced the window frame guide. After getting everything back together and driving the car I heard a faint whistling at the top of the window which wasn’t present prior to the replacement. Upon inspection I noticed around a 2mm gap at the top right corner of the window frame guide where the window frame guide should sit against the aluminum trim. I tried loosening the 3 compensating socket bolts on the sides of the door and my adjustment helped a little, but I am still left with a gap. My next plan is to heat-up the area with a heat gun and gently pull the area where the gap is… would this be a bad idea? Anyone have any noninvasive suggestions for addressing this?

Hi, thanks for the diagram. Any idea what part 14 is? I’m seeing oil around that area and I’m trying to investigate. Thanks.

P1531 Actuator triggered, no active position. - Open circuit in triggering wire. - Open circuit in B+ supply. - Actuator faulty. P1689 is not a valid code for MY1999 C2. Perhaps check again?

Hey everyone, first post here and fairly new owner of a 99 C2. I've finally been able to run some diagnostics with the Durametric and I got the following fault codes: P1689 - Control unit faulty P1531 - Camshaft adjustment bank 1 I suspect P1531 is a result of a faulty DME, but that is simply a guess. I should note that I've had issues connecting to Durametric and seeing the fault codes in the past (evidence of some kind of DME issue?) Also, I've been experiencing a bit of hunting idle and what feels like engine shuddering (misfires?) at idle. I've cleaned the MAF, TB, and replaced the IACV. The vehicle had an aftermarket radio installed by the PO which I've recently upgraded to a double din unit, but I haven't changed any of the wiring. I'm in need of some troubleshooting help. Would it be worthwhile to start with a replacement of the DME relay? Thanks all! dro

Thanks, that's what it was. The headlight tray was damaged and the connector wasn't being held in securely. Replaced the tray and all seems good now. Thank you

Did you reset the codes and now they have come back? Is it misfiring when idling? While driving part throttle? Wide open throttle? What coils and plugs have you changed? If you have changed plugs, how did the old ones look? Oil covered? Eroded? Smelled like gas? Sooty? Are you on fresh gas or two+ month old gas? Do you have a Durametric? Can you monitor some live values like fuel trim, camshaft deviation, etc.?

Still Fighting the misfire, local shop checked some things and found that my battery cable, the bolt that goes through the fire wall and starter / alternator cable needs to be replaced ( starter also ) before they go farther with diagnostics. $720 for diagnostics and $4000 to replace above parts (parts included) Payed for diagnostics and did all work myself. Still same problem - misfire on cyl-1 and sometimes on 3 ( misfire on 4 was just loose coil from my sloppy install ) work in progress 😞

UPDATE: SOLVED - I was finally able to bring the car into my mechanic. Basically, they replaced the driver side door lock actuator. Here is the part number. (uro parts door lock actuator 8N1837015C) On the passenger side it was just a broken clip that they replaced. So, problem solved (for now).

Picture for sympathy... Tires were cracking so I picked up the wheels off FB (plus I was feeling optimistic 😐)