Sudden Engine Failure no warning

I'm not sure what level of problem it is but I'd rate severe/critical Hello, this Is my first post I recently purchased a Boxster S 987 2.7 M96 2007 - RHD Long story short on how i got it is that it's a family members it died suddenly the mechanic said it needed a full engine replacement and they obviously didn't have the money for that so instead of them essentially getting rid of it for a few hundred because they don't have the space to house it or funds to repair it we bought from them so they could afford a replacement vehicle. But as for the vehicle problem as I have been told. The check engine light came on, they drove it home and let it sit for about a week until they could get it in for service then on the 15min drive to the mechanic the car died suddenly that there was some white smoke and the car came to a rolling stop and had to be towed, and apparently had some oil under it when it was picked up from the side of the road. The car is currently on a slight slant approx 20-30% incline of driveway (front end up) so I'm not sure if that is having a effect on the oil level test in the instrument cluster which reads as Full Car is under roofing and car cover, I have enough tools at home for working on it short of having a hoist (I have not attempted to start the vehicle) I did some research and found alot referring to the AOS I did some inspecting of the engine yesterday and have come across large amounts of oil (Pictures attached) in each side of AOS hose ports and as well fair amounts in the throttle body itself and in the rubber boot attached to said TB, (I have also come across no signs of any form of removal for inspection other than some trim parts still disconnected which makes me think very little physical inspection has been done and possibly only scan tool readings. My scan tool shows only codes of 2 cylinder misfire (cannot recall which but one of them was cylinder 4 if that helps) I am wondering if anyone has any insights and tips of what other things I should take a closer look at and possible causes. (Fingers crossed not Engine Boreing) as I am no expert and have been a porsche owner for more or less 3 days P.S my thoughts as new first time owner of this visualy beautiful vehicle is that the person who designed the layout and engine location is in fact a menace to society and should be fired out of a cannon into the Sun. 😊 (Rear window Glass not vinyl)

The mechanic said it needed a new engine, did they say why? If this mechanic is familiar with Porsche cars, I would hesitate to assume they mistook a bad AOS for a destroyed engine. I have heard of, but have no first hand knowledge of, AOS failures that dumped so much oil into the engine that it hydrolocked. Though that seems unlikely to happen during a cautious drive to see a mechanic about a known problem. At any rate, it has already been looked at by a mechanic who has apparently made a diagnosis. Find out what that diagnosis was. Edit: also, double check what you have. You said 2007 boxster S with a 2.7 m96. An S will have a 3.4, and I believe a 2007 should be an m97. 2006 could be either, but 2007 was all m97.

I have no information on why they said it required a new engine it was only at the shop for less than a day before they said that, but i dont think they were familiar with porsche cars, there was signs of a few trim pieces disconnected but no signs of any engine parts being removed for inspection so im not sure if they simply checked a plug and found oil or went by what the obd2 system said and just estimated, the car had the engine light come on and then sat at home for about a week until it could get booked in, then on the way there it died, im not familiar with Porsche computers do they have a engine protective feature that shuts it off when it detects a big problem? or the possibility that the influx of oil soaked some of the plugs causing it to missfire and causing the engine to shut down by some protective feature ?. this is what the Reg info gives the and the compliance date is 06/2007 the Vin WP0ZZZ98Z7U703674 if you wish to check for yourself. also update: i removed the manifold sleeves yesterday and found large amounts of oil sitting in the top of the manifold, which i cleaned out, and removed the AOS and opened it and found the fabric/plastic filter? located in round section with the spring unit similar to a thermostat (image below of my unit for part # you can see the split in the top of the photo) so that explains the large amounts of oil in the system so i am currently looking into a new part and will be removing the plugs next to inspect for oil on them. Overall im not sure on if the mechanic provided any information but a few hours and a little research and i found a very obvious parts failure. so maybe its just not a car they are familiar with. thats not to say there isnt a much larger problem that caused it to fail but this is just the first thing i have come across And than you for your Reply

Was Looking through the Service Book and came across this. not sure what the added numbers are, top one seems like a new engine number but what about the one under it

Based on what you've found so far, I think you're on the right track. You obviously have a bad AOS, and it's likely fouled out the plugs, so you've got the right idea changing the plugs out with it. A lot of the plastic lines that connect to the AOS are probably really brittle by now, so be careful with them, but they may break anyway. They are available, but the long one can be a pain since it runs under the intake. Something else to think about. All that oil was dumped into your cats, so before you put them back on and cook the oil into them, clean them out the best you can. You can just soak them in water with dish soap then rinse them. Take the o2 sensors out first. For the print out: The first number is the VIN of course, item 10 means it's a 2007 year model. The second number is the model, Boxsters and Caymans are 987, 311 is for Boxster base right hand drive. The fourth number is the engine, M9720 is the 2.7L m97. I don't know why the reg info says m96, but it's definitely incorrect. That's good because the m97 is much less prone to IMS issues, and the 2.7L doesn't have the bore scoring issue that's somewhat prevalent in the 3.4L. It's generally a robust engine, so here's hoping the mechanic was just unfamiliar and you can get it going again with an AOS and some plugs.

Also, get yourself a Porsche specific scan tool. I have a foxwell n510 and it works well. A durametric cable is also a good choice if you want to data log, but you have to have it connected to a laptop. The iCarSoft ones are apparently OK, too, but I don't have any experience with them. You can also get the knock off PIWIS tools, but that's probably overkill for most people. Though at today's rates, a single trip to the dealer to recode something will pay for it.

i have the Foxwell nt301 its what gave me the fault codes of cylinder misfire will i need to recode anything?

i didnt have any issue removing the AOS in terms of plastic plugs they were all fine and dont seem brittle, at least the top ones were not im not sure for the side one has i havent removed it because i didnt need to take out the unit, at that point i had removed the the manifold sleeves, the rubber seals for both, the throttle body the hose connectors from manifold sleeve 2 that run to the aos, the throttle body itself and the rubber boot attached to the other end of the throttle body, and cleaned all of those aswell as the inside of the manifolds where the oil had pooled apart from aos which needs replacing, i am waiting for some tow straps which should arrive tomorrow to pull it forward a little onto level ground before i look at removing the plugs, so you recommend i pull the O2 sensors to clean aswell as the cats? we did notice some oil drippage from the exaust as well as some inside the end, so what do you think the best approach is for cleaning the cats, will i have to drop the whole exaust system ? or is there a cleaner i can spray in from the rear or a easy way to flush them. Thanks for your input definitely hope im on the right track and that it isnt something that is irrepairable

I just mean the main cats, the ones that are part of the header/manifold. I wouldn't worry about the ones that are part of the muffler. You can just let them soak in a container of water and dish soap for a while, then spray them out with water. It's not going to be critical for getting the car running, but all that oil will cook in there and you'll end up with a check engine light for cat efficiency. This is really only a problem if you have emissions tests where you are. The cats are a couple thousand each, so if you need them it's best to try to save them. You could pull the front o2 sensors out first and look at them to get an idea of how much oil is in there before you commit to taking them off. It's not a huge job to remove/install the exhaust manifold, but if the bolts are really rusted up, a broken one can turn into a major chore. Sorry, I don't know what those hands written numbers could mean.

Good to know, Thanks for the heads up on the bolts, might be busy today so not sure how much headway so ill follow up more once i get the ball rolling.

It does seem like the AOS but have you tried draining the oil to see if there are other issues?

yeah plan to drain it and give it a change and new filter after we do the plugs just waiting on the some better weather

With the weather being bad today, might take a look at removing the trunk release button panel because those are broken and need replacing and might take a look at removing the radio unit, because it apparently some times works and sometimes doesn't so im wondering if theirs possibly a loose connector in the back of it, because fuses are fine but also wouldn't be fuse if its a intermittent issue, Ordered the new AOS which should hopefully arrive in the next day or two if im lucky, put everything else back together yesterday since it was all clean now. just hoping whatever hoses and parts still has leftover oil sitting inside will get flushed out and burnt up after running it for a little bit since with the new AOS there wont be more oil actively coming into the system. also apparently its quite easy to view the block from behind the seats and inspect the belts, so might look into removing that cover as well to see for any obvious signs of part failure that i cant see from top side.

The trunk release button is pretty easy to replace. There are knock off versions on ebay that honestly are just fine and much cheaper than an original piece. Mine was also broken when I got the car and I replaced it with one from ebay. No issues more than a year later. If you don't have a bose system , the radio is easy to replace as well. Any aftermarket unit can be installed, and there are trim/wire kits available to make it super easy. If you have the bose system , it's more involved because of the fiber optic stuff, but still doable.

not 100% sure but it is the unit that has the Nav system aswell, i found a half blown fuse (didnt even know it was possible) in the rear of the unit so im hoping that will be the fix im hoping these dont need radio codes

If you had the bose system , it would have bose markers on the speakers. Also when you pulled the head unit out it would be pretty obvious. With the bose system , everything is connected via two orange fiber optic cables, so there's very few other wires connected to the head unit. If it looked like a typical head unit with a bunch of wires for every speaker, then it's not the bose .

We do have a tiny thread on replacing the 987 audio unit, and a few people have a bit of experience doing this. You might want to take a look. PLEASE do look through the entire thread (I know it's long, I should put together a condensed one, but I usually explain what I tried even if it failed so people aren't condemned to following in the same footprints..) Outstanding Tech Contribution! - DIY on installing an... It's being shipped tomorrow. It will be replacing a Rosen headunit that replaced another Rosen headunit that replaced the CD30 radio. I realized I never use CD's in the car so having that was a waste of time, and I can save money and still have SiriusXM by using the Android Sirius app (which is... www.planet-9.com

mine is the pcm2/2.1 not an issue removing it, and reinstalling it. quite simple, but im hoping the unit wont need replacing and that it was just the fuse that was the cause, ill find out when i hook the battery up next .

remove aos, clean all the oil from intake, replace plugs (clean coils only at this point, but good idea to replace if you fix the car), do an oil change, save the old oil in a clean container for further future investigation/analysis including the oil filter! Start it up and I bet you're good to go. I blew threw 2 AOS in my 987. To a non porsche mechanic an engine blowing a HUGE amount of white smoke just non stop looks like a blown engine and it will of course misfire and keep dying. That is not how you diagnose a Porsche . You put your hand over the open oil fill cap and feel for vacuum. So many cars wind up at auction thinking "BLOWN ENGINE" which is just a $300 fix.

Jimmy, since you are replacing the AOS, I would strongly suggest that you replace the 'accordion type hoses' that connect to the AOS, one goes to the top of the bank 4-6 (passenger side on your car..) and the other one goes to the air intake hose. The one that goes to the top of the engine is a bit tricky as it goes under the intake runners, but once you remove the engine cover behind the seats you will have enough room to replace it without removing the bank 4-6 intake plenum. Keep in mind that these 'accordion hoses' are at least 15 years old.. Good luck on your repair!

are you referring to the vent lines that connects on both sides of distributor pipe (3 way pipe in image) or the other line that has a bracket the runs across the top of the engine or are you referring to different hoses Also thank you for the help and luck! new aos arrived from Porsche so now im just waiting for a nice day

yeah plan on replacing the coils depending on how bad they are, will be giving it fresh oil and filter though, but will see how we go, my oil filler cap is this type, will it make any difference for feeling vacuum and just to confirm im looking for strong vacuum or am i looking for a little or none at all?

Hello Jimmy, yes, the 'accordion hoses' I was referring to, are the ones on your picture. I am glad you got them as these have relative thin walls and become very brittle with heat and age.

the ones on seem pretty good, when i was inspecting them and cleaning them, they might have been replaced at some point in the past because they look pretty pristine

great news!

unfortunately the radio unit still isnt working after replacing the bad fuse, im not sure if it needs a code or something because the display is completely off,so i dont know if getting power or if it only powers on after you enter the code, because i assume i should be able to turn on it on with only the ignition on, i took off the knobs to see if they were faulty but they seem okay, so yeah just gonna look into that today, and put in the new boot/bonnet release switch panel

For reference my unit looks like this (not my image) PCM 2.1 RDW P/N: 997.642.141.10

i mean i guess its possible for it not to work because the boot/bonnet release unit isnt plugged in (as i am waiting for new one to arrive) if it connects the whole system together, but i cant imagine it would affect it, either way might know more ones i actually fire the car up, but will probably put it on the back burner while get back to the one i was working on, before i got it

I find it hard to believe the boot/bonnet release unit (I assume the one in the door sill) has anything to do with the PCM . As an old physicist/EE - a fuse is a bi-state device. It's good or bad. I've never seen one "partially blown" - if there is any break in the element - it's blown and won't conduct electricity. That only happens if the current through the circuit exceeds the current the fuse is rated for. Unless the wrong fuse was installed (a lower current rating) that never happens unless there is physical damage of some type to the fuse, or the circuit has a problem causing it to draw more current than it was designed for. Looking at your photo: Is the horizontal section circled/arrow pointint to it - the half-blown part? Did you check this with an Ohmmeter? It looks blown to me - not partially - but entirely. IE - the "blown" fuse is a big clue something is wrong with the PCM, and the fact that it was the fuse in the connector on the back of the PCM (fuse of last-resort so to speak) to me means the issue IS the PCM has problems. ------------------------------------------------- Earlier in this thread, you mentioned you were looking at diagnostic codes using a Foxwell NT301. Unfortunately - the NT301 is relatively limited in what it can read - it can read OBD-II and EOBD-II codes - emissions-related codes required by most countries to enable emissions inspections. What it doesn't do is actually read the Porsche codes which are stored all over the vehicle in control modules. The 987 probably has 10 or more control modules (things like each door has one, there is a central one to direct signals to the others and interface with the hardware in the car, there is one for the convertible top on a Boxster, there are several for the ABS/PSM, there's one for the throttle, there is one for... well, you get the idea.. the car is basically a complex computer system interfacing with mechanical controls.) To do any actual diagnostics on a 987 you need to go beyond OBD-II/EOBD-II codes. You need to know what the modules in the car think is wrong, what they're receiving as input signals, and what they're doing with those signals (making windows go up/down, opening the throttle, etc.) You're pretty much blind without having that info. If you have those codes (called "P" codes) - they can take you a long way towards figuring out what the issue is. We have a diagnostics forum.. Porsche Diagnostics and Programming - and I can humbly say we're probably the best resource on the web for that sort of information. Besides having tables of codes with explanations, and evaluations of different diagnostics tools, we have a number of members who really know what's going on and what many of the P-specific codes really tell you. Right now - the sort-of-favorite diagnostics tool here seems to be the Foxwell NT530. It's certainly not perfect, but it does have particularly good diagnostics for the 987 series of Porsches. If you're going to continue down a DIY path it's a worthwhile investment.

thats a partially blown fuse, the fuse wire has heated up causing the metal the start to deform but then something else stopped the connection causing the connection to remain in tact but not broken, i imagine if i had tested that fuse it would have had a complete circuit but it would only be at a lower voltage than normal, i understand engine codes im fairly well versed in old bmw systems and (how infuriating they are) have specific tools and programs for that, but i dont currently have a plug for porsche systems as im uncertain if a k+dcan diagnostic cable adapter would work on porsche protocols if i had piwis software. so id have to look into getting one that supported it. which would be more cost effective and provide a more thorough analysis on and issues, what i dont seem to understand is why the cluster says pcm failure when it didnt previously when it had a bad fuse, but does now with a fresh fuse that is supplying power, yet with power the unit shows no sign of powering up, i figured if the unit had a error in a connection it would show you on the display or say a certain function was unavalible or something and not just not turn on at all, like with a computer when it has power generally it will turn on even if it wont start at all it will still power up and fail, could it be something like it needs to be resynced or recalibrated, that will only happen once the engine is actually running with all the units powered on, as opposed to just the ignition on, but thanks for the information, if the unit is fried id have to open and look for signs of damage like a blown capacitor but ill worry about that later.

Should be easy to test. If you don't have another person handy, just put something moderately heavy in the passenger seat and try it. But the only reason I could imaging for this being a thing is if someone rewired the PCM 's power wire into the airbag controller. Not likely or safe. Hummm....Does your car have an ASK amp under the seat?

well looking from the wiring at least on the harness's to the radio nothing has been spliced, and possibly im not sure? there is a module under the driver seat which i think is a phone module, PN: 997.646.209.01 but i have not check under the passenger seat yet. Also just want to add another photo up close of the half blown relay because its such a wild thing to happen in my mind, where you can see what i mean by the wire heating and losing form and giving it from afar a almost staircase like effect

Stepped fuse elements are a thing... it's not the sign of being worn out or failed. For example: https://www.amazon.com/COOPER-BUSSMANN-ATC-10-ACTING-pieces/dp/B00LQSFPO6 ATC/ATO Automotive Fuses, 20 Amp Fuse skycraftsurplus.com Etc.

I was resisting posting a photo of one.. I have a box full out in the garage. The difference in this type of fuse design is it's used a lot for a "Fast Acting" fuse. It fails quickly when more current is drawn than it's rated for. "Normal"* fuses - the ones with the U-shaped elements fail a bit slower and don't react as critically to an overcurrent. A brief-low overcurrent with a U-shaped fuse generally will result in it surviving. Not so with the Z fuses... if you look closely at the element in the fast-acting fuses - there are multiple steps made up of a thicker piece of the fuse connected to the next one by a thinner piece. The thinner bit is what fails, and typically the thicker piece drops away from the melted part, making it pretty easy to spot the blown fuse. * = the Z design can be used for a normal speed fuse.. but it's commonly used for fast acting fuses. It has multiple points of failure - meaning one is likely to fail quickly.