Sparkplug change and lots of carbon build-up 987.2 2.9

This past weekend I finally got to replace the spark-plugs and coils on my 987.2 with the 2.9 engine and 90k miles. It turned out to be a bear of a job, not because of all the steps to actually get to the plugs, but because all of them were more or less seized. Especially the plug on the left/driver side that is at the front of the engine (#4), which of course is the hardest to get to. All the plugs had a decent amount of oil and carbon on their threads. In the end the whole job took close to 6hrs, with breaks to run to Napa or HomeDepot, for the right socket and penetrating oil. I also stuck a bore-scope into all of the cylinders, and found a LOT of carbon on the pistons. Below are some pictures. How worried should I be that I have some bigger issues? Note the thread on the above, almost as if it was cross threaded by the PO. Lots of oil on this one. The hardest one to get out, with lots of carbon. Probably the worst of all the pistons. Most pistons look like this

Looks mostly fine, somebody just left the plugs in too long I think. That first plug does look a bit messed up, I might run a spark plug thread chaser down that cylinder to make sure the threads are clean and okay, and also on the others to see if you can get the carbon out. Use a vacuum to remove anything that comes off. I'd run a bottle of BG44K fuel system cleaner through the tank, and then use a bottle of Techron every now and again. Don't overdo it but it'll help with the carbon.

Fellas, I’ve looked at spark plugs pulled from the heads of cars since 1971, across all makes, even Renault. I don’t see anything wrong with those spark plugs except usage from repeated firing. One thing Porsche owners should do is balance their maintenance vigilance and consternation with how the car is running.

I wonder if the previous owner oiled the plug threads before installing. I remember mine were dry with only mild carbon on the end.

If it wasn't clear I totally agree, at least for the plug electrodes. My comments were related more to the plug threads: the first plug threads look a bit flattened maybe? Could just be the picture but he mentioned potential cross-threading so that's at least worth a close look. Also there's a lot of carbon in the hole threads so that's probably worth cleaning out with a chaser just to make install and removal easier. That said, that might be difficult given the plug access: last thing you want to do is cross-thread the chaser, lol. So use your judgement. There's some carbon on the piston heads, but that's pretty typical and fuel system cleaner will help with that. New plugs should go in dry: they're plated so they don't need anti-seize.

I just realized that the oil on the plug threads probably was from the penetrating oil earlster used to help extract them. So the presence of oil doesn't indicate any problem.

Combustion is dirty, always has been. I saw many engine tear downs, in the 70’s tear downs were common. Also common? Buildup of carbon on the underside of exhaust valves, again all car makes. Fuels are cleaner than they were in the 70s, but they aren’t clean enough to prevent carbon.

Totally agree with that conclusion. Carbon is the result of any and all combustion. Unless you’re building rocket engines, and not being a propulsion engineer at NASA, I wouldn’t doubt that Carbon is not a byproduct in those also. Even the cleanest burning, most efficient internal combustion engine is really not all that efficient, resulting in Carbon buildup. Those plugs look pretty normal based on the miles and number of times they have fired and arced. Doing mine soon, ordering this weekend from fcpEuro , so I will compare my results and post any significant differences.

I don’t know if this is your first time going in for the plugs. If so, I have two helpful recommendations. The cover for access to the plugs took me a while to get back in because there was no way I was going to bend it even slightly. When I finally learned the puzzle, I told myself next time I would use painters, tape, and mark the orientation front end back end and top. That tape is quite easy to pull off after you reinstall them. The second thing I would recommend is a variety of extensions, short, long and mid length. Each plug removal is easier with a unique approach using the different shaft lengths. PS Not a bad idea to put a pencil magnet on each bolt you remove from those plug covers as you remove the fasteners.

I still have a Porsche technical bulletin from the 944 which states you should add Techron , I don’t remember the intervals, but I agree with you. I usually do it twice a year.

I was thinking about eventually doing a walnut blast, as I'll hit 259K tomorrow in my 2.9L - so surely I've got carbon up the wazoo. I think I'll give some BG44K a go soon and see if I notice any positive change.

You shouldn't need a walnut blast unless you've got unusually heavy build up on your intake valves. Reason is I'm pretty sure the 2.9 still has port injection. So you've got fuel constantly washing the intake ports and backside of the valves and you shouldn't have any significant carbon build up there. That's usually a problem for DFI engines because the fuel gets injected directly into the cylinder, so there's nothing to remove intake valve carbon. I mean, walnut blast won't hurt, but it's probably not necessary: something like BG44K should be sufficient.

How much is a walnut blast going to cost? Also, how many more miles do you think it’s going to be before it needs a tear down regardless of buildup?

You're correct, @gubi - our 2.9L is indeed port injection and a key reason for the longevity. I'll skip the walnut blasting; frankly I was never sure if it made any sense to begin with. @ Boristhespyder - Let's hope never, right?

Hey, maybe you’ll be that famous Volvo driver, I think he put 1,000,000 miles on a P 1800 I believe it was.

How hot, warm or cold was the engine when you stared?

As an older guy, I wonder how good that driver’s seat was north of 300k?

I did some math on that Volvo high mileage achievement. The guy really liked to drive. He averaged over 150 miles a day for many decades. Part of the achievement was the car itself, but a big part was simply the amount of driving he liked to do. There is a Porsche 996 turbo which has logged over 750k miles. Quite an achievement as well. And it has even seen track time. Here is the story from a while back. How do you get a Porsche Turbo to 647,000 miles? It's all about seat time - Hagerty Media The 996-generation Porsche 911 Turbo is a serious machine, but one owner loves it so much he drives it year-round, including in the snow and on track. www.hagerty.com

The engine was cold.

This was my first time, I got the car 2 month ago. It clearly had some deferred maintenance issues. I never fully removed the heat shields, just pushed them down and out of the way.

Thank you all for your feedback, I'm feeling a bit better about it all now. Will be running some techron before the next oil change, which is soon.

Haha...I was thinking the exact same thing. No doubt in need of some "reconditioning"!

It becomes even more interesting if you add in that he did over 450,000 miles in a newer Volvo sedan that Volvo gave him when he reached 1,000,000 miles. That would mean in 52 years he drove a total of 3,750,000 miles. That's roughly 71,000 miles a year, or ~200 miles a day. That's every day of the week. I'm guessing he was single. And not involved in community activities, or anything except driving the car. I wonder if he was independently wealthy since it would seem unless his job involved driving 200 miles daily he wouldn't have time to hold down a job. The 996 turbo - gotta hear that story and do the math.. looked at the article and they did the math. Just under 100 miles a day. Not even a smidge like Irv... As far as the Volvo seats - I owned about 6 P1800's through the years - and the seats lasted about forever. Instead of horsehair in the seat (which German cars were still using in the '80's) - they took a design from Swedish furniture of the time. 3" wide elastic straps in a crossed/woven pattern as the basic springs, then about 2-3" of fairly high density foam. The seat bottoms were removable and identical driver/passenger, so I used to swap them every so often. Worst case - have the foam redone - cheap and easy. They were really the most comfortable auto seats I've ever experienced.

Does the car blow blue smoke and/or require additional oil between changes? If not, I wouldn't worry about carbon buildup. It's going to happen, especially on a 90k motor. I would definitely apply anti-seize to the new plugs so this is the last time you'll ever have to fight as you back them out.

I've checked the oil level several times in since I own the car and it has been steady at one bar below full. Also had an oil change done just yesterday and will continue to monitor it. As for blue smoke, I had noticed a blue cloud at startup 4 times in the 10 weeks of my ownership, but usually it's all clear. Those always happened after I had moved the car around in my driveway before. I have a new AOS unit that I got when I bought the car and will replace it this winter as preventative maintenance. I did not apply anti-seize as it is not recommended, I think simply replacing the plugs more frequently should do the trick.