P0305 and P0303 after new O2s installed

Now, my new=to=me '07 2.7 w/ 81k miles is missing and stumbling after warmup. I've only had it a month, and replaced O2 downstreams on both banks iaw P0431, only got worse... Now get P0305, P0303, and P0300, and got blinking CEL as I got home and shut her down. Gonna check plugs and coils even tho posters say it is rarely that; I was careful putting those new oem Bosch downstream O2 sensors in. Dirty Maf? If plugs look fine, what is usually the next suspect? Tank is half full of Shell V-power. Oil Level is at the top, above the upper thin line marker. I do not see a lot of smoke after warmup. I searched the forum, but this seems strange for a coincidence ... VVS Vanos, Variocam solenoid, Valve lifter solenoid all mentioned here; are they the same thing, that 9A1... part#? Should I replace the 9A1... sensors, or punt and tow to the busy indie, missing Xmas at Mom's? Thanks for any input! Otherwise I love this Cayman...

Not sure if I can help much. Unless I'm backwards the downstream O2 sensors are there for monitoring the cat function. That would have been your first message. It's the upstream O2 sensors that mixture is controlled to though. Replacing the downstream ones shouldn't have affected operation. It sounds like your oil is over full. It never should be over the full bar. You shouldn't have any smoke after maybe a puff on initial start. I'd adjust the oil level first. If you're getting any smoke after warm up maybe the plugs are fouled. I'm not sure what you mean by 9A1 sensors. 9A1 is the engine model released in 2009 to replace the M97 model used up through 2008. The M97 has similar sensor but I wouldn't suggest starting to replace those until you've got it a little more defined. Just replacing parts on these cars can get pricey fast.

First thing I would do is drain one quart of oil and recheck level. Good luck.

Thanks folks! Happy holidays, BTW... Drained ~1/2 qt, and dash oil level gage is still all up, over top thin line. Will repeat until block above line is dark... Opening the engine compartment in a bit, my 1st time. Diver down!

Don't forget to drain the oil.. Drive it for a bit then let it sit for a few hours. Then take a reading ... This doesn't sound like a typical oil overfill unless it is REALLY overfilled but I hope that is all it is.

How the oil came to be overserviced could be an issue. If someone just put to much oil in then correct the level and hope that a bit of driving takes care of the rest. If it's been this way for a while there may be other consequences like fouled plugs etc. to correct. However, if the engine made oil you could be looking at a failed oil cooler, head gaskets etc. If it's something like this the oil won't look right. Might want to save a little of the drained oil just in case. First step either way is to correct the oil level. The level should always be between the two thin lines delineated by the arrows. It's ok to be down one segment. Why I really wish there was a backup dipstick. With the stupid estick you can't tell if you're over by a hair or a couple qts. It just lights that top segment over the full line.

Thanks again! I really enjoy reading these helps, as it tempers the disappointment...:thanks: Estick is now up to the top line, and not over. It took draining ~2 qts to get there, and the oil is dark despite the dealer saying it had "a fresh oil change and brakes"! If there had been a physical dipstick, I could've just pulled it and seen for myself the color and level. I took the intake with the MAF and the two across the engine top off, and there is no oil contamination there, nor cracks. Applied CRC MAF cleaner to the MAF. I could not spot any obvious vacuum leaks, but did not run the engine. I have done all I can do that I am aware off without test eqpt except pull a plug and coil, so that is next but I doubt that will solve the issue. Plug wires are shiny blue new looking and the assy belt looks fresh, so this lil' pup has had some maintenance. The AOS was dusty but seems intact. Air filter was filthy but not the worst I've seen. Am I correct in that the fuel filter is in the tank? Only parts I've replaced so far are the back O2s. Last time I drove the car Friday after installing the O2, the CEL blinked as I got home, so i hope I am safe to disconnect the MAF wire and see if it runs better then, unless y'all think that is unwise. Looks like 'over the river and through the woods to Grandmother's house' ain't happening in the 987 this year, but at least the local indy is well- regarded here in So. MD. Anymore tips you think of are welcomed, of course, and thanks .

2 qts over is a bit much. That might be enough to have gotten it up into the workings to have churned the oil around enough to darken it assuming the oil was indeed fresh. As long as it just looks like dark oil instead of a dirty, frothy milk shake from water in it and your not down on coolant you can probably skip that path for now. Hopefully oil that was potentially in the cylinders didn't do any lasting physical damage. I'm a little surprised that there wasn't a little oil in the intake around where the AOS hose connects. Pretty common. Sounds like the AOS is ok. From the sounds of it the intake path is ok. Never tried running without the MAF sensor . At the least you'll get another code or two. I don't know if it has fault acommodation to run without or not. This is the point where I'd probably record what codes you have, clear them, say a prayer for luck and try running the car for a while to see if getting the oil level right makes it happy. Maybe now that it's not flooded in oil it will clear itself and run right. If not at least you'll know what you have now that the oil is correct. I don't know what damage might have been done by this much overfill. It can get ugly once the oil level is above the cylinder bore. Hopefully it wasn't enough to do lasting damage. If it all does work out and run I'd change the oil. This fill has probably been beaten to death. Good luck.

Any idea if this is the original MAS? Unplug it and see if it changes anything. If it doesn't it might be the MAS. Mine had the same issue. New MAS fixed it. Also do you have a way to clear the code. It may run OK after that?

Tks Greywolf, Y'know, I forgot to mention that the last time I drove the Cayman, the battery barely had the power to start the car! Research has told me that these cars are hard on batteries, and that a weak battery causes trouble. Could this be the source of the above symptoms? Gonna hook up my Ctek 4.3 charger tonight ! Any advice on type or brand of battery? Thanks

I don't know that these are any harder on a battery than every other modern car. Even when off they're doing something it seems. There's a couple long threads on battery replacement that covers pretty much all the players. From memory the Walmart, Interstate and Autozone ones seem to be the most common choice. An H7 frame size (or whatever they call it) should fit perfectly without fuss. The slightly larger H8 will fit from what I understand but you have to finagle a nut in under the battery tray to secure the hold down. For whatever reason Porsche didn't put one at the last hole. At least on the 3.4L engines. I don't recall if the 2.7 had a smaller battery or not. When I replaced the battery I went with an Autozone H7 Platinum AGM . Fit perfectly and has been fine so far, 6 months or so. Just remember to pull off the little plastic plug and plug the vent hole on the side not used. It's on the red plastic positive (+) cover. I'm not familiar with all the CTEK models. If that's just a maintainer it might take a while if the battery is down as far as it sounds. A regular charger would be better if you have one. Then keep the CTEK on whenever the car isn't going to be used for a few days. A low battery seems to do all kind of weird things on these cars. I don't recall reading of this specific issue but who knows. Worth a shot and you need to get the battery happy anyway.

Have you checked the coolant level and color?

Coolant Level is good, color kinda pink. AOS lines and bungs at intake had a drop or two of oil. Got a coil out and it has cracks, plug worn out but grey, connector looks good, tube is clean: No 6. Thinking I'd buy coils and plugs, and with the battery charged I may yet arrive in FLA...:drivingskid: