WP0

No, as long as you're doing the work, you replace them all. . . do you just replace one spark plug?

RennListUser01

OK ... so, hcamp replaces plugs when it was unnecessary, then there is an issue, apparently with one coil that occurred in a suspect time following the plug change. A shop determines #5 is misfiring on Friday, but then next week determines #3 and #5 misfiring. Shop then replaces coils and plugs on both cylinders. Given the plugs were new and only #5 was determined to be misfiring, why would a mech replace two plugs, and two coils? Does anyone think it likely that two coils failed at the same time? That the plugs were suspect?

Remember, only the coils on 3 and 5 were replaced, right - along with the plugs that just been replaced? Why not all of the coils? Why not replace the plugs, again? I don't get it.

If coils were $50-100 apiece, I would replace them when they failed. If this wasn't logical, why would the testing device read out plug by plug - ie identifying the specific failure, why not just read out "This is a Porsche and is special so replace all coils just in case and/or because the parts and labor are so expensive?."

ClassJ

Seems to be a reasonable thought train.

I despise coil packs. With my E90 BMW, I fought and argued with the dealer as coil packs went bad one at a time under warranty.

Over a 5 month period, I had three coil packs fail. One at a time. They replaced them. One at a time.

After the third one went I replaced the other three at my cost at home to overcome the madness.

RennListUser01

So, scratching this a different direction ... which manufacturer coil on plug devices are better? Denso and NGK make them ... are these better worse than whatever the OEM crap appears to be? Where are the OEM coils made, and by what company? Where are the various aftermarket coils made, by company?

RennListUser01

I like your solution - although the circumstances are a bit different.

I assume you kept two of the ones you preventively removed in the trunk? JIC?

hcamp19

Porsche recommends that the plugs be replaced at 30k miles or 4 years. Although I now think that is overkill, I was doing what was recommended and concurred to by some on this forum. The shop DID put new plugs in both #3 and #5. I think you need to carefully read my post from yesterday again. Some other items to consider:: 1) These plugs are not easy to get to and impossible to work on when the engine is hot. 2) You have to remove the rear wheels and heat shields to get to the plugs. 3) To properly evaluate a repair, the car should be running at operating temperature and driven. It was reasonable for the shop to repair it the way they did. If it hadn't been for the absolute weirdness of the problem not following the plug and coil from #3 to #2, I would have done it myself and saved the money. I had already changed all the plugs once (which means having the coils out). BTW, these coils from Pelican or FCP are $75.00 each, $85.00 from this shop. I don't want them to replace anything that is not showing a problem, that's just additional and unnecessary labor and parts expense.

Noah Fect

The onboard diagnostics are garbage. Speaking as an EE, it should be the most trivial thing in the world to detect which of 6 coils is associated with a misfire condition and report a specific error that tells the tech exactly what coil to replace. Instead, Porsche has elected to display all kinds of completely random error messages that have nothing to do with anything that's actually happening, leaving the tech to sort it out at the customer's expense.

The coils are not that expensive in the grand scheme of things, so it makes sense to just treat them as wear items like the plugs themselves. Swapping the coils out every other plug change interval makes sense to me. The part #s are constantly being revised, again because somebody doesn't know what they're doing, so this will also provide some assurance that you have the latest/greatest parts.

ClassJ

Honestly no. The failure would always be the same. Pull onto highway (engine under load), CEL pops up. Engine runs on 5 cyls. Pull over. Restart car. Engine runs fine. CEL would clear after a bit.

I gave up keeping parts and tools in modern cars. I have basics, a compressor, and tire plug kit. But thats it. I do keep some additional items in classic cars.

Back on topic...my 991.2 T has under 1000 miles. Its approaching 4 years old. (yes I need to drive it more, no I am not insane, just have very little personal time in the past few years).

There is no way I am pulling plugs yet. Porsche's age based service guidelines are largely a gift to dealers. Plain and simple.

WP0

I guess people's definition of easy differs: IMO, jacking the car up and removing the rear wheels is as easy as it gets!
Also, people's definition of expensive differs: IMO, replacing 6 x $75 = $450 every eight years is rather cheap.

ClassJ

EE here as well. Do these cars use 4 wire coil packs? I recently used a toyota 4 wire pack for a project. It has a feedback pin that works quite well. It basically tells the ECU if it fired or not. Very simple and straightforward. Porsche could make reporting misfires simple. Unfortunately there seems to be all sorts of schemes for this like looking at crank position sensors etc.

The car should be able to know if it fired the plug, opened the injector, etc.

Noah Fect

It's crazy that the car doesn't know this, even without feedback. The E/I characteristics during a misfire look nothing like they normally do. There's simply no excuse other than incompetence or indifference.

Tier1Terrier

Yeah. I've only changed my plugs once a 4 years & about 10k miles. Given what a pain in the but it is to change plugs on these cars, I'll probably go the route of changing the coil packs preemptively on the next change in another 3 years.

RennListUser01

Hmmm ... so, it sounds like there is no data available on which coils are prone to failure, allowing folks to choose which to use to replace failing coils?

I've changed a lot of plugs - on cars, outboard motors, motorcycles, etc over the years - on a couple of worn out engines with point type ignition I've seen oil deposits, but I never have on a high energy ignition system, including engines with 100,000 plus miles of pretty hard use. In every photo of a normally maintained and otherwise normally operating Porsche engine, I have only seen perfectly fine plugs ... I guess I just don't understand the desire to replace operating components, unless the car is in warranty and it is required,

Working the logic in reverse ... if you don't maintain your car yourself, it is going to cost a fortune regardless - so, why not wait till the coil or plug stops working? If you are not going to drive it when this happens, it doesn't really matter, does it?

If one is really worried about plugs becoming stuck in the heads, aren't there penetrating lubricants that will help? And, is this just rumor or is their data - not the anecdotal stuff - that plays to this tune?

I'm trying hard to adapt to the Porsche mindset, but this sort of things makes me spend a lot of brain cells over too many martinis.

spiderspider

I recently did my plugs on my 2014 at 20K miles and that #5 plug felt like it did not want to come out. Had me sweating a bit andI even stopped and to think about it for a day. It did come out but with much more torque than I'm accustomed to on a sparkplug job. I didn't see any thread damage or corrosion, so I don't know if it's just the nature of the beast. But yeah, I will keep to the 4 year interval. And be very sure not to over-torque.

RennListUser01

This, then, begs another question. What does the curve look like on a plug getting stuck in a head ... ie, does a plug increasingly get more stuck over the first x number of heat cycles then flatten out? And, is it related to time or heat cycles? If not changed at 3 years or 4 years does the "stuckness" not increase, or increase more slowly?

Should one use PB Blaster prior to pulling the plugs?

Someone noted new plugs have a thread coating to help? Would it be better to pull the plugs immediately after delivery and put antiseize on the threads? What would a drop of oil do - given this is done all the time on other engines?

It sounds as if Porsche has different timelines for different markets? This doesn't seem to follow any engineering logic?

Think of all the other questions begged. What percentage of dealership income is related to unnecessary maintenance? Has this increased over time as Porsche slowly convinces owners of the specialness of their cars relative to other cars?

Sigh ...