Originally Posted by Noah Fect

The concern is that their threads will seize in the aluminum housing if left unchanged for too long. Dissimilar metals are never 100% compatible, in terms of thermal and electrical properties. Antiseize can help with that, but it can also affect the plug's ability to shed heat, as I understand it.

Probably the #1 reason is the guaranteed employment clause in the dealership license agreement with Porsche. Somebody has to pay for all that free espresso, the 18' gas fireplace, and those awesome service bay doors that open in like 300 milliseconds when you pull up to them.

Originally Posted by NI3

Hope this follows my gut feeling that it is minor. Good luck Brother.

Originally Posted by RennListUser01

This is an interesting mystery! Really irritating to the OP, though. We feel for ya, brother!

So, the car ran fine for 35 miles, then spirited driving ... THEN malfunctioned.
- multiple warnings point to something upstream of the coils? (I don't gave a frame of reference on 911s-when one coil is bad, does it feel like running on 5?, and does one bad coil cause all those other warnings?) Seems like more than one cylinder is affected.
- heat caused something to fail (like a position sensor)
- vibration caused an upstream connector to slip apart?
- vibration caused a wire that was moved to rub?
- vacuum hoses? (these are easy to forget or to put on then pull part way off while closing up from the work)
- brake fluid ... hmmm ... does this service get close to wiring in the frunk?
- fuses all good? (something shorted after spirited driving?)
- plugs from same "batch?"
- plugs not correct range? wrong length? (I know, OP - not trying to be offensive, just riffing)
- any water involved that could affect electrical connections?
- fans reconnected?

OK - everyone is thinking of "the answer." Hope it is something simple. Here's a link for a coil pack problem - sounds a bit like yours - coil failure starts ECU light show ... https://rennlist.com/forums/991/1065...s-wrong-2.html

Question from a newbie - why would one change plugs with 10,000 miles if the engine was running ok?

Originally Posted by RennListUser01

Fingers crossed for ya!

Now, looking back on it ... better to just leave things that "Aren't Broke" alone? :-)

Yeah, x Porsche says 4 years or 30k miles!?

So, we're now we're maybe talking odds on:
- wire to the coil (somewhere?)......maybe
- bad coil (must have failed after the 35 mile and during the spirited driving)....probably
- plug itself (new plug failure?)....possibly
- plug not fully seated (a long shot, but I've done this before on non-ECU based engines and it doesn't run right)....Nope, torqued 'em sure
- coil not attached well enough (or something in the boot causing?)...double checked that after issue

Can one "meter" the coil prior to replacing?...the coil can be bench tested but one needs to know which 2 blades/terminals to check resistance at

Hmmm .... broad categories?

1. Something randomly failed, or became disconnected, etc during the spirited driving.
2. A new part you installed failed.
3. Something you did during installation caused the failure, but only AFTER 35 miles and then spirited driving.
4. Some else is causing #5 to misfire.

This is FUN - probably wrong word? Probably would NOT be fun if it was my Porsche!

Originally Posted by hcamp19

I had it towed to the shop on Friday. The mechanic hooked it up to his diagnostic and said all he showed was a miss on #5! Note my earlier posts with roughness on #3 and #5 before and after I had switched the plug and coil between #3 and #2 with no change (yes, I cleared codes in between the switch but not after so the mechanic would see what I was seeing. My thinking was if the switch moved the issue to #2, I would put a new plug and coil there and then address #5). He will get into it on Monday and let me know what he finds. Thank you all for your concern and stay tuned (bad pun not intended)...

Originally Posted by RennListUser01

Why would one replace all the coils?

I could certainly see replacing the coil that is identified with the misfiring cylinder, but all of them? Is there a way to test the coil?

Originally Posted by RennListUser01

Not sure I understand - what is the Porsche procedure for a failed coil? I would assume it is replacement?

Been thinking about past ignition issues - had a V6 engine just instantly develop a "miss." Carbon fiber center spark plug wire started "breaking down" (not transferring high voltage) electrical energy from coil to plug. Carefully examined, but no visible damage - replacement fixed. Did not replace others - worked fine for another 7 years and 120,000 miles. Just a vignette.

Anyone have photos or engineering analysis material on construction of these coil over designs? Is there a specific failure mode - ie is it really the coil part, or internal connection fittings between the coil and the plug end?

And, anyone reviewed coil over failures to see if they are more common on one brand or another?

Finally, I just took a look (newbie) at the various spark plug offerings ... is there really a CHOICE between four ground, two ground, and one ground styles? I can't find mention of the specific plug in my manual but all options (copper, plat, double plat, and iridium all show single ground designs). HCAMP - did you replace with single, two, or four ground design?

Originally Posted by WP0

Yes, it's my impression that it's generally accepted amongst Porsche 911 DIY'ers to replace all coils every other spark plug change.

Originally Posted by RennListUser01

Not sure I understand - what is the Porsche procedure for a failed coil? I would assume it is replacement?

Been thinking about past ignition issues - had a V6 engine just instantly develop a "miss." Carbon fiber center spark plug wire started "breaking down" (not transferring high voltage) electrical energy from coil to plug. Carefully examined, but no visible damage - replacement fixed. Did not replace others - worked fine for another 7 years and 120,000 miles. Just a vignette.

Anyone have photos or engineering analysis material on construction of these coil over designs? Is there a specific failure mode - ie is it really the coil part, or internal connection fittings between the coil and the plug end?

And, anyone reviewed coil over failures to see if they are more common on one brand or another?

Finally, I just took a look (newbie) at the various spark plug offerings ... is there really a CHOICE between four ground, two ground, and one ground styles? I can't find mention of the specific plug in my manual but all options (copper, plat, double plat, and iridium all show single ground designs). HCAMP - did you replace with single, two, or four ground design?