Double checking -- Coil packs and spark plugs?

Hi gang, One of those situations of ask twice, order once. I'm pretty sure I'm headed for coil packs and spark plugs , but just wanted to double check before ordering. Admittedly haven't had much time to drive Cherry ('09 987.2 2.9L Boxster ) much this month and finally did so. First, I filled the tank with about a half tank of gas (Speedway, which is admittedly not top tier yet not a no-name). After about 75 minutes of largely highway driving, I pulled over for about a half hour and then got back on the road for about 7 minutes. I then pulled over to make a phone order for some awesome BBQ. When starting the engine, it sounded ever so slightly lumpy and threw a CEL ("Visit Workshop"). Turned off the car, but the CEL message stayed. Engine seemed fine. Drove for another 10, let it sit for 30 at the BBQ place, and then drove home gently at 65-68mph on the highway. Engine drove smoothly as it ever has, and I even hit a staggering 32mpg highway. Finally pulled the codes today via the PIWIS 2 . I hadn't done so for at least a few months (maybe since I reverted my muffler to OEM). Here's what it showed. DME CAN codes were: P0300 Misfiring summation fault (exceeds limit value) P0304 Cylinder misfire detected (exceeds limit value) P0431 Warm up catalyst efficiency below threshold bank 2 (exceeds limit value) First, I'm guessing the P0431 might have been a leftover from the exhaust work I did this summer/fall, so I'm not too worried about that. Guessing it was an exhaust leak? If it comes back, I'll have to investigate. But if I'm correct, P0300 might be an indication of multiple misfires of various cylinders (not great!) and P0304 is clearly cylinder 4. A while back and after starting the car after lots of very brief start-up/shut-downs (moving the car for a parking space), at one point I did notice some lumpiness a while back when starting the car, but things smoothed out. Sunday was the first time it had ever thrown a DME CEL under my watch. As Cherry has less than 500 miles to go to reach 260K, I have no idea (yet) per the car's history if the plugs/coils were changed. I've heard of people getting Xmas tree stuff error messages when plugs/coils go, but I think that's more of a 981 + thing. I'm assuming that both plugs/coils must have been changed out at some point, as the car seemed to be dealer maintained for the first 10 years of its life. In short, as I've got major surgery coming up in just a bit over two weeks (and even need to get a car inspection ideally in the next 48 hours -- which I think is doable given I cleared the code), I figure I should just replace the plugs/coils at $270 while I can still wrench -- as I won't be able to seriously wrench again until mid-July as I'll be recovering from my operation. As those plugs are not fun to access, I figure just do everything at once ( Bosch plugs, Beru coils). Any thoughts to confirm my plan, let me know. Cheers and thanks.

Generally any time you get a specific cylinder misfire code you'll have a P0300 random multiple misfire code to go with it. Plugs and coils are a great place to start even if they turn out not to be the culprit..

Given the symptoms - coils/plugs are in order - all of them (do it once..) My experience replacing a single coil has never been good. As soon as I replaced the one that had recorded misfires, another one would go bad. I learned that lesson. All of them - do it once. FCPEurp should be able to get them to you overnight even using their normal delivery (stuff always gets to NJ overnight, and they're about midway between us..) You don't need to be worrying about the car during or after your surgery.

First of all, we wish you speedy recovery on your incoming surgery. At 260K miles, coils & plugs are probably overdue even if assumed to have been replaced. Put heat shields this time around if you have not done yet. It does not only protect your ignition coils but may also give a barrier protection from burning wires in an event of cat or exhaust manifold stress failure

Backing up what Don said about the coils. Professional shop mechanics have told me for a very long time to replace all coils never one. In fact the mechanic who told me that was directing me to do so before each plug had its own coil. The old 5.0 mountaineers had split coils I believe they were 4/4, even then he said “ never do just one of the 4, I have had consistent issues with only doing one affected side of the two packs”. PS the heat shield replacement will be easier if you mark them with painters tape for front and top before removal. There was no way I was going to bend mine, so it took a little extra effort to figure out the circuitous route it takes to get them back into place.

Depending on your location, emissions testing will fail you if you've recently cleared codes. I think it takes many hours and miles running to build enough history. Luckily I don't have to deal with that in my county.

I don’t care what location you are at, if you take it to an emission center shortly after clearing a code it is going to 100% fail. You will need to have multiple ignition start stop events, you will need to get up to highway speed back off of the accelerator and let it go down to just about coast speed several times and you will also need to put on perhaps as much as 300 miles. I went through this last year when a loose gas cap threw a code right before my emissions test. Wishing you the best surgical outcomes and a speedy recovery, perhaps you can get an extension on the emissions test.

Yes, my clumsy wording meant to say "if emission testing is required at your location". Even in states that do testing, often it isn't required in rural, less populated counties. They likely just check for "check engine" idiot lights.

Hey gang, Thanks for the confirmation. I totally agree, and it never hurts to ask before an expensive purchase. Can't hurt anything except my wallet. I was planning on doing it at some point, but the misfires are forcing my hand to do it now and quickly before surgery (especially as I won't be able to wrench, but I should be able to drive Cherry about a month post-surgery). Unclear if the P0300 (random misfires) were caused by a failing cylinder #4 plug /pack, but yes -- I'm always from the school of thought to do all at the same time -- especially to scientifically rule things out. I do try to save money on wrenching, but this is a bear to access and it's the price we pay for running a properly weighted mid-body engine. Do it once, do it right. LOVE the idea of painters tape for heat shield orientation. 987.2s come with heat shields, and they are indeed fiddly from what I remember. Just as importantly, thanks for the warm pre-surgical wishes. Surgery sucks and I'm pretty anxious about it, but hopefully I'll get through it just fine. Just hoping and praying that I don't have the shingles neuralgia again -- as that was worse than anything post-surgery. As a former med student -- if you're 50+ and haven't gotten a shingles vaccine -- I beg of you to go get one NOW. I could hardly wear a shirt for four months. Not kidding. You guys are correct about the code clearing and inspections. Here in MA, you need a solid 100+ miles on the engine post-CEL clearing -- and I suspect that's pretty universal here in the US. Thankfully in my case, Cherry is a 2010 and she just reached her 15th birthday in 2025 (as I write this). This means, no OBD connection anymore or emissions inspections -- it's just a quick visual inspection. Cherry has failed inspections before as I had just cleared the codes (likely after PIWIS 2 work, not due to engine work as I generally do a "clear all codes"). However, MA will give you a failed sticker so you can safely go drive for the next few weeks and put the 100+ miles on the car for a re-test. Will keep you guys posted how things go. I have to go back to dealing with my E30 BMW 'vert today for pre-surgery and pre-sale wrenching (not fun with 20ºF temps outside and unheated garage) but hoping to get that order in ASAP. Cheers.

FWIW, for future reference (2010 987.2 2.9L), I just ordered 6X from FCPEuro : Porsche Direct Ignition Coil - Beru ZSE052 ​ Porsche Spark Plug - Bosch FGR5NQE04 ​ I didn't order the kit, as I already have dielectric grease here and the kit offers no savings. It's just there for convenience. Although I have a swivel set and a spark plug socket, I figured - just order the GearWrench one (GEARWRENCH 3/8" Drive 6 Pt. 5/8" x 6" Magnetic Swivel Spark Plug Socket - 80546) on Amazon and don't mess around -- this will be my dedicated one for the P-cars. The least thing I want is for something to get stuck. Free shipping and hopefully FCPEuro will get this out quickly -- maybe fast enough where I'm wrenching in just a few days.

Just watch the plugs that are most forward toward the front of the car, they all require finesse and a gentle touch, but those plugs are at a weird angle. It’s best to use care to make sure that the porcelain isn’t damaged upon removal and if that was all that happened, it would be a good day. A variety of extensions and combos of said extensions depending on plug is invaluable. PS Surgery makes everyone nervous, that’s completely normal. Once you go to sleep the rest is just recovery, you wake up and it’s behind you.

Oh wow, @Boristhespyder - I know about respecting plugs, but didn't realize these were potentially rough per removing. I knew access was totally fiddly as I could see first hand. Could be entering a hornet's nest, but it needs to be done. Staying away from anti-seize this time around and going to strictly torque to spec (assuming I have the clearance to do so) and not go by feel. Not going to play around with the wrong torque values and the like. Hopefully I won't have to go back in for a good long while. I don't like the idea of being "put to sleep," let alone my not looking forward to my surgeon cutting back into the same exact scar I had - it's already a sensitive area to begin with. Finally, the opioids were horrible post-surgery. Hopefully I'm getting better at surgery; this will be my second surgery and the third time I've been put out via anesthesia. One day at a time, I guess.

It sounds like spinal surgery? I’m a club member too if that’s the case. The entire process is stressful, I’ve been on both ends of it. I have assisted surgeries with C-arm fluoroscopy. You’ll probably be on morphine drip afterwords, crazy dreams, as you know. As for the plugs, do not fear the job, respect it. The best advice I can give is to be as square on each plug as you can, regardless of what combination of angles and extensions it takes to reach that goal, you will do fine. I also made sure to start each one by hand of course as I always do but you can’t put your fingers in that deep obviously so it’s a touch feel situation with the extensions and extra vigilance. I have a snap on finger tool for extensions that I used. It sounds like you have already have done them anyway. I did not use any anti-seize because the plugs came out quite easily from the factory after a decade and it’s not recommended as you know . My coils had barely any miles on them so I just did the plugs.

I’d suggest getting a boroscope and looking inside the cylinders while the spark plugs are out. Check for bore scoring.

@sstearns2 - Thanks for the suggestion. Certainly not a bad idea, especially given that boroscopes are so inexpensive these days. If it was a 987.1 (except '05 base), I'd certainly do that but I'm admittedly far bit less worried about such with the MA1 2.9L engine. Given the currently stressful pre-surgery time crunch, I'm likely just going to focus on just getting the plugs and coils done and save such for another time. However, we'll see where I'm at when I get it up on the lift.

all the best with your recovery and procedure! just to add to the feedback so far, the coils will usually have visible cracks on the plastic "shell" quite apparent to spot visually if they are indeed giving issues. you can see the pics of the cracks sampled in my post sometime back: https://www.planet-9.com/threads/9a1-100-000-kms-60k-miles-water-pump-belts-and-tensioner-and-more-condition.239661/?post_id=2127635#post-2127635

Funny that you mention cracks in the coil packs. When I was purchasing my ‘08 Boxster , the report from the PPI noted cracks in the coil packs and they suggested replacement. I thanked them for their ‘attention to detail’ , purchased the car and knew that one day I would do the plugs and coils myself, saving a huge chunk of change. Fast forward to last month when I got under there and replaced those items. Hmmm, no cracks to be found on any of the coil packs. So I can only guess that since there is a known issue of cracking they decided to include that in their report, without any visual/visible evidence of cracking. Nothing worse than finding a problem that doesn’t exist.

The lack of any cracks does NOT means they are not bad. It's very common to have failed coil packs with zero visible damage. Its the symptoms the car is exhibiting, and what the codes say that matters, regardless of what they look like

thanks for sharing guys.... its always an item to keep an eye on. WTFChuck, I didn't realise that it could go back to having no cracks! ICNU, yes you are absolutely right... the techs at my local indy would always do 3 things - ask me if I had any signs of misfire/rough idle, check the physical coils and plugs and check the codes.