three culprits I can think of:

- over-temp - cyls go oblong and pistons score cyls

- bad aos - no vacuum to crankcase so piston rings don't function properly; pistons score cyls

- over-rev - all bets off

I don't think engine mods will have much effect unless they push you into a lean condition and start making thinks hot, or timing goes off. from what I've seen (check out insite's wideband o2 post) the ecu tends to keep even a heavily modified engine in the safe zone.

Yes but aren't m96 inherently hot-running even with OEM parts? If you're going to push the engine harder with aftermarket stuff, while using a 'conventional' oil, and no other augmented safeguards, aren't you inching the car closer towards unsafe temps on a fairly routine basis? In other words, If there is an 'event', the usual margin or buffer is no longer thus reaching a threshold breaking point more likely.

p.s.
i'm not an engine engineer I just play one TV.

well, a stock 996 3.4 engine is making 300 hp with the same cooling system, oiling system, bottom end and heads as a bolt-on modified 986 3.2 engine making 265 hp, so I don't think you are pushing any limits there. as long as the ecu can manage the mixture and timing which all evidence shows that it can.

people say these engines are built to rev, but perhaps a life spent at redline is a contributor - bits moving faster, more heat, etc. modifications tend to encourage harder driving?

56,000 mls, coolant ok, no leaks or anything. Driving up the mountains/canyons here engine ran a bit hotter but did not overheat.
AOS, I think it may be on the way out since I had a couple of times just a little blue smoke on cold starts, maybe 5 times over the last 6 months...
Never overreved, Durametric checked.

Hmmmm, this week I hopefully know more!

Car goes into the shop July 25, will update then.....

Right on; more redline more stress; but higher M96 rpm apparently puts the ims bearing in a more stable symmetrically loaded condition and piston ring oil film strength is better. Perhaps this where the "made to rev came from". Maybe it should be have to rev?

Ok ya'll!

Car is back home and runs as smooth as ever..... Woohoo!!

Turned out to be 2 blown coil packs...... Nothing else!

What makes this so weird is that the sound the engine made was really scary. Larry, my new best friend and THE man at the dealer thinks it might have been a stuck lifter and suggested to change the oil even though mine is only like 3,000 mls "old".
I will follow his advice.

He also is just rebuilding a GT 3 RS engine (over revved), the man knows his stuff!

Thanks all for listening and helping!

Later,
Andy

Great news, especially when one considers all the other things it could have been. Enjoy!

Two coil packs and all that racket went away? Man. You must have had a big shipment of positive Karma coming your way.

awesome!...

You guys have no idea how happy I am. I was really scared, not gonna lie. On the other hand a 3.6 would have been nice......

Anyways, there is more to tell, not tonight, though, enjoying my scotch right now.

Wow -- engine out of balance with 2 cylinders down?

was there any codes? I'd love to know how they knew to try replacing the coil paks.

glad that was all it was

thanks for sharing --

mike

Come to think of it I haven't replaced any of the original coil packs. What are the risks of not doing this? I recall speaking to an indy once who said he didn't beliueve in replacing these for this engine.

As long as the outer insulation skin of the coil packs have not been compromised by heat cracks or mechanical damage so letting moisture through into the electrical windings, there should not be any mileage / time degredation to the performance of the packs.
But once the outer insulation has been breached, moisture, salt + corrosion can cause the internal electrical windings to short down to ground, thus causing the common misfires on individual cylinders.
If you clean and inspect each coil every service (12 monthly) you can spot any cracks or damage to the outer skin and replace the coil before the insulation breakdown causes you to lose a cylinder.

Very cool to hear, and glad nothing crazy. I sent a message to another member on here with the same symptoms you described to check his coil packs.

Yeah, again, happy! I was so surprised as well, that knock sound was really bad and I still can't believe all is good. As mentioned earlier the tech (Larry) suggested to change the oil and recommended 5W40. He is a real veteran in this trade.
BTW he is rebuilding a GT3 RS engine right now and had a few others lined up as well. They are really busy with engine work.........

And to top it off they cleaned my car really well, looks fantastic!

From one Utah fellow to another I say, "that is great news". Where did you have the work done? Someone like Larry would be good to have in the back pocket. Glad you are up and running again. The weather is going to start getting perfect for top down driving in the canyons. Happy day!

Strong Porsche SLC, Larry is there since the '50s, I know him for 20 years.

Strong replaced my battery on my 997.2 when it was out of warranty and failing cause all kinds of, as we say in Utah, "heck"... for free. Though expensive for an oil change, I'm generally very pleased with them ("sweet spirits"). Though I don't always get a Cayenne or Panamera as a loaner, they have rented me a car from Enterprise a couple of times during service and/or brought me back my car at home/work when done. Bought 3 cars/traded them back since 2006. Don't even consider Garff. Wonder how the Steve Harris dealership will do now that, I think, Garff has it in their paws.

Update!

Changed the oil and inspected the filter very closely, was super clean, nothing to be found in there!

Engine runs better than ever.

Strong Porsche is the place to go to, never had a problem with them and always got a loaner.