na4life

Well, I’m now on my third 991.1 engine. First engine got horrible bore scoring at 16k miles. Replacement engine got scoring only 2k miles later.

The first replacement (2nd engine) they only replaced it with a short block so I suspect faulty fuel injectors were causing the wear since they just transfer those over.

now I have to decide if I should just sell the car or pony up for a fidelity platinum warranty and risk it. Thoughts?

desmotesta

You last statement is confusing to me. What risk would you be taking with a Fidelity Plat plan if you decide to keep it.

As for you running into 3rd Bore scoring issue on same car, the chances of that are minimal, if not zero. If it does happen, you have to ask what other factor is part of this equation (operator error). Not blaming you for any of this, just mathematically, you have to start eliminating factors.
I would keep the car as you know this car and it now has a new engine.

Charles Navarro

We had a crate 3.4 987.2 engine score bores in a race car in less than 10 hours. Had a faulty injector. Likewise, we've seen instances where a shop used a factory shortblock on a 997.1 and keep the same injectors - engine scored the same cylinder bore again only 3,000 miles later. Injectors were tested after the failure and found to be bad. It's bad enough we made injector replacement required on rebuilds in the directives we provide customers.

Out of curiosity, do you know if it was the same bore that scored the second time?

na4life

Yep, same exact bores were scored on the second engine (3 and 4). They didn't replace the injectors the first time around so it sounds like that's what happened. On this latest engine I implored them to replace all the injectors and also change airflow sensors just in case (since it sounds like the typical failure mode is either leaky injectors or the mixture being somehow way too rich). This does give me some peace of mind though that I didn't just get super unlucky. Likely the injectors were the culprit then.

worf928

Charles, can you describe the linkage between a bad injector and bore scoring?

Charles Navarro

One of the ways they can fail is that a bad injector won't atomize the fuel properly and ends up washing the cylinder bore down. As fuel isn't a lubricant, lack of proper lubrication ends up killing the cylinder bore. They can also leak, flooding the cylinder with fuel when then too washes away the lubricant.

We see this happen with engines with nikasil bores as well, however it's the piston rings that get wiped out in that scenario.

Charles Navarro

Since it was the same cylinders I would agree that the injectors were the likely culprit for the second failure. Very good thing you got them to put new ones in the last time around.

AdamSanta85

What are your thoughts on BG 44K fuel injector cleaner? Supposedly it is the best of the injector cleaners.

Possible preventative maintenance?

Charles Navarro

I use a bottle of Driven Injector Defender + Booster every other tank of gas. But then again, in my area, there are no easily accessible top tier gas stations nor are there ethanol free fuels. If you have top tier fuels, I'd probably say you are safe to use a bottle every 3,000-5,000 miles (I'd say at least every 6 months).

What is critical is that whatever fuel system cleaner you use has the additive Polyether Amine (PEA). That's the strongest cleaning agent you can buy.

Also if it takes you more than a month to go through a tank of fuel, you really need to use some sort of additive to stabilize the fuel unless you have access to ethanol free fuel like REC90. Bad fuel kills injectors.

BlueShell

Are you referring to this?

Charles Navarro

Yup, that's what I use. We also sell it as well.

https://lnengineering.com/products/j...tle-70056.html

There is also a version without octane booster, but there is no price difference, so why not have the octane booster. I know in my GTI and Mercedes I see a noticeable increase in fuel economy on my regular route (60 miles each way from home to the shop), but both are turbo charged, so the extra octane is probably why I see that improvement. Even more so in the winter when stations have winter blends which are much crappier than summer blends.

blepski

Charles, in these instances of faulty injectors that you've seen were there any tell tale warnings in the form of rough running and or an engine malfunction light due to a misfire or overly rich mixture?

Charles Navarro

I don't know what the limits are for adaptation on the later cars, but on an M96 or M97 it can add or subtract 20% I believe before it will throw a CEL. What ends up happening is that the ECU starts adding more fuel to compensate which makes the problem worse.

worf928

Interesting. Thanks. All I see is 928 engines and bore scoring is pretty rare - and even-more-rarely catastrophic - even with serious wall washing. One might suspect that the Lokasil process just doesn't work nearly as well as the last-century cast Alusil cylinder blocks.

sunspot2013

So sorry to hear of your troubles. Did you have a CPO warranty or did Porsche cover the repair as an exception/goodwill?