garrett376

Just a heads up for those who own high mileage 958's: ignition coils are not listed as a maintenance item yet when they get old and fail, a complete electrical shutdown occurs of all systems and the car is not drivable.

Out of the blue upon engine startup the following occurs: check engine warning with flashing check engine light, Auto-start/Stop failure, ACC failure, ABS/PSM failure, engine hardly idles.

My 11 Turbo has 96K miles on it with impeccable service of all required items, yet this single coil failure just about ruined a 760 mile road trip that was supposed to start the next day. Thank goodness it occurred in the driveway the night before we were to leave, versus somewhere in the 117 degree heat of the desert.

Since this failure is preventable, I suggest 958 owners consider replacing them as a maintenance item as their failure will lead to an undrivable car. Or at a minimum, carry the few tools needed to diagnose and replace them and keep a single $45 spare new one on hand and hope only one fails at a time! Mine was lucky #4!

TexasRider

I thought the coils were a Porsche call out service item. But good to know.

deilenberger

Garrett, just curious, what change interval are you using on the spark plugs?

MountainStone

Did you replace them all as a preventative measure or just the failed coil? I'm surprised a single misfiring cylinder causes such chaos...

garrett376

I replaced just the failed one... on a friday night there was only 1 coil in the entire city of SLC that I could get my hands on the following morning... With that said, 7 more will be arriving this week from Sunset.

And yes, I am also amazed at the complete shutdown that occurred.

garrett376

I use the recommended 30K/4yrs interval. I'm at just 2yrs/16K mi on the current set.

TheUnscented

Which diagnostic tool did you use to find the offending coil? What did you determine was the best source for the coils and the plugs?

garrett376

I had a cheap OBD2 code reader that I carry in the car that told me it was cylinder #4.

The emergency coil was from a local auto parts store and had the .13 part number. I bought my 7 coils, part number with a ".14" at the end, from Sunset Porsche. The parts in the car were original .10 part numbers.

D Fan

I agree with garrett. Germany coil usually only last 70k to 100k max. The Bosch coil on my wife's BMW failed one after one at 70k miles. My 955 has 100k miles now. I am going to replace all the coils next week because I noticed a few misfire lately. Coil is so cheap now ($20-$30 each). I will suggest replace all of them at 90k along with the spark plugs.

Joe Weinstein

An '11 CTT whose records I have, had all the coils replaced, once at around 30,000 miles, and again at 50,000 miles, each time for diagnosed misfires.

FutureClassic

I just turned over 80k and ordered plugs and coils as a preventative measure. After reading this thread, it seems like a no brainer to stay ahead of a potential breakdown!

deilenberger

I'm at about 91,000 miles and no misfires reported yet. On the turbo - plugs are a 30,000 mile item, and a bad plug can overheat a coil which will cause the housing to crack and the coil to eventually fail. Running the plugs longer is a false economy (pound foolish, penny wise..)

GTS958

First time contributor and long time reader.

Agree. I have a 13 Cayenne GTS. It's reaching 72,000 miles. We had the 60K service a year ago with new spark plugs.

Over the past several months electronics went crazy. First the PSM failure / Auto Stop START failure happened followed by Check engine light, rough idling, poor acceleration. Generic codes read P2308 and P0353. We isolated it bad Cylinder 3 ignition coils. Deleted the codes but after driving for a day, they all came back so it's probably real. Had all 8 replaced after reading this thread. Reset the codes and the lights went away. Idling became smooth, great acceleration again, PSM failure lights and auto stop start lights went away. Driving normally for the past week. Dealer quoted the job at $1,200. OEM ignition coils purchase by yourself is north of $500. Took me about 5 hours to do the exchange, test drive, and put everything back. If you know exactly what you are doing, then probably much quicker than that! I had on time and only services from certified Porsche Dealerships up to this point and found several screws broken along the beauty covers and cracked ignition coil covers before I started. Just to say, nobody takes care of your car better than yourself if you can do some work!

Not sure if in the end it was worth it because it took so much of my personal time but it's definitely an experience!

RAudi Driver

I had a coil pack go bad. Car was still drivable on 7 cylinders. Only a misfire code. Everything else on the car worked. I could turn off the car and restart and the coil pack would work again for the day. I carried a spare in the cayenne with a 10mm socket, 1/4" mini ratchet and a flat head screwdriver. The day it finally went out for good, I swapped it out in 10 minutes and was back on the road. Came home and installed the remaining 7.

Good idea to always carry one in the car with a 10mm and flathead screwdriver if yours are due to be changed soon.

CK.GTS

When I went to start my GTS this morning, I got the PSM Failure and Check Engine error show up, along with the Start/Stop functionality disabled. I'm assuming it's the same issue with the coil packs, but I guess I can't be too sure until the codes are read.

Am I OK to drive it to my independent mechanic's shop? It's about 30 minutes away, but the rough idle has me a bit concerned. If it's OK to drive, I'll be taking it in tomorrow to get the coil packs replaced. I had it on my list to do as a maintenance item this year, but I guess the car decided to remind me sooner.