daveyator

So, I bought this 2017 991.2 GTS Cabriolet in Dec of 2020 with 9200ish mi on it. Had a history of normal maintenance and recent oil change prior to sale. The car "asked" for service in January of 2021with 14600mi and Porsche advised me to get a 30K/5yr service per Porsche recommendation. I balked a bit but ultimately had it done which includes, among other things, spark plug change. When I got the car back it had a marginally rough idle compared to how it was before. I pointed it out but was assured the car was fine. Indeed, when the car got warm it was almost gone. After a month of so of this, I brought it back to the dealer and they dutifully took it back, analyzed it, even brought me back to chat with the tech who again assured me all was well but did acknowledge the slight rough idle. Car has been completely normal acting since then until I recently brought it for routine oil service. Being still bothered by this "idle" thing I asked to have it checked out. To their credit, they agreed to even though it'd been nearly 2 years since the major service. They find mis fire codes on cylinders 1, 3, and 4 if I remember and further find a bent electrode on 3. They replace all the spark plugs again just to be sure and now the car idled smoothly like it did before. They didn't charge me for any of this except the oil service. I leave the dealership and get about 20 mi toward home and when passing a car, the engine misses very abruptly for a moment then is fine. I decelerate a bit and then accelerate which induces a more violent missing episode followed by ECM, and PASM fail messages and the engine missing horribly except under the gentlest of acceleration along the with the "drive carefully to the nearest workshop message. Obviously, I returned to the dealership and they wound up giving me a loaner so they could analyze the car. A week later I'm informed several cylinders are washed out with internal corrosion and pitting, oil is entering the cylinders which is causing the mis fires due to oil rings failing, and that I need an engine replacement. Gasp. At this point, Porsche is replacing the engine under CPO. I've never tracked the car and have only done a few autocross events as far as aggressive driving goes. I guess I'm concerned about resale value, ramifications of a new engine etc. I've never had this happen before and frankly still can't believe it. One person even pointed out that I'll no longer have a "numbers" car although not much of a factor with a modern 911 I think. Chatting with the service manager, he told me that there's been a slight uptick in low mileage engine failures.

subshooter

I see it as a plus. You get a new engine on a six year old car.

I am a bit suspicious about the diagnosis though. Seems odd. Who knows though how the original owner treated the car through break-in etc.

PV997

Agreed, if anything a new engine would help resale value rather than hurt it. If it was a collector's item and people cared about numbers matching that would be one thing but these cars aren't rare.

What bothers me is they didn't give you a root cause. I guess they are claiming the rings failed but how does that happen on multiple cylinders at the same time on a low mileage car? And what caused the internal corrosion and pitting? Oil shouldn't do that. Sounds to me like a cracked block or something along those lines and coolant got into the cylinders.

WJGreer

Agreed. I can't see that happening as a manufacturing defect unless it were widespread across multiple cars, suggesting an issue with the assembly robotics or the cylinder forge or something. But as a one-off problem it doesn't make sense. Something bad happened to that car before daveyator got it.

It's wonderful Porsche is covering the engine replacement. Imagine the situation otherwise.

MingusDew

Sweet. Free engine.

DC911S

Nothing wrong with getting a new engine. I had to get a new one on my 2018 GT350 with only 6K miles due to oil consumption problems.

daveyator

Agreed on the above comments. I asked directly about coolant issues, head gasket etc. They claim none were found. There was a 718 spyder there with 900mi getting a new engine with similar issues. Starting to wonder about Porsches metallurgy with recent engines (recent being within the last 5 years or so) based on my conversation with the service manager. Another odd question, how do I know I'll get a 450hp engine or are the horsepower differences in the lower end (base,S, GTS) software as opposed to actual engine differences? Sorry if a naive question but I do wonder. Even if the car was driven hard before I got it, shouldn't these engines take a fair amount of aggressive driving outside of blatant abuse?

DC911S

The base, S and GTS have different turbos. Same turbo housing but the compressors are different. How do you know you will get the right one? Trust I suppose.

IXLR8

My Porsche friend was over this past week for pizza and I mentioned to him, "if anyone has to open up an engine or transmission, I really have to wonder about the reliability of the car". That of course provided it has had one owner that looked after it and did not abuse it.

But my other Porsche friend who bought a used 997 had the engine replaced under warranty. He later found out that the previous owner had lent the car to his kid, no further comment.

HardRider

Does anybody find it coincidental that after the first maintenance it missed at idle, then they go back and the engine is destroyed. The dealership fked this engine. Cylinders don't wash in 20 miles lmao. Corrosion happens in 20 miles. I hope Porshe gets that engine evaluates and refused to reimburse the dealer for their screw up... Maintenance in the end is what destroyed your engine...

1CEBITN

The initial symptoms sound pretty consistent with bad coil packs, especially the misses on multiple cylinders. Not that it matters now but would have been interesting to see if they would have re-done the plugs plus the coil packs if any of this would have happened. Sorry you have to deal with all that mess but hopefully they get it all fixed up for you and you've got a new engine in a 6 year old car. FWIW, that kind of thing can happen to just about any car these days. The flat plane cranks on the Mustangs and the C8Z06 have had premature engine failures, I know a couple people with stock RS3s that had motor replacements under warranty as well. The BMW guys have a hard time getting BMW to cover anything like that under warranty but they've had some odd issues too over time.

HardRider

This failure was driven by highly trained Porsche certified technician. Corrosion and pitting takes years to occur unless car was under water. So that is a lie. Engine ran smoothly after new plugs, but didn't with new plugs two years ago. 20 miles after leaving dealer engine fails. Probably cross threaded a plug, broke a plug and piece of ceramic left in it. I easily bet $50K if that 911 was never at that dealership that engine would be running today without issue.

DR911s

I'm liking HardRider's version, and 1CEBITN's version, too, and now I'll add my own in response to the allegations of corrosion within the cylinders... either cracked castings or leaking gaskets allowing coolant into the cylinders, or someone making a huge mistake and adding coolant where the oil should go.

The good [great] news is that Porsche is going to replace the engine. The part numbers and work documentation ought to confirm that the correct GTS engine is installed, assuming they are replacing the engine as a factory built complete unit and not as a long block to which the dealership will add the manifolds and turbos and accessories from the blown engine. I wouldn't expect that to be the case here because the turbos are likely contaminated with debris.

DBH

Porsche will only be replacing the "short block". All other ancillaries such as turbos, software, etc. will be reused from your existing engine.

daveyator

Yes I see your point. The engine is not in the US so they told me last Thursday it will be at least 3 weeks. Additionally, they say Porsche doesn't always ship all the extra parts needed for the change out. If they have the additional parts on hand they can start when they get the engine. Otherwise, they will have to order the additional parts.