pkurzenhauser

I'm new to the Renntech forum as a poster, but have used it for looking up stuff. Unfortunately, I also have experienced the cylinder scoring problem in my 2008 Cayenne S, with less than 48,000 miles on it. Here are the details: Back in January, my wife noted that her car would run rough once in awhile, but when I drove it, I didn't notice the problem. In February, it started misfiring significantly, and the check engine light came on, flashing, which the owner's manual says to stop driving it as soon as possible because the catalytic converter can be damaged. She was just pulling into the driveway when it came on flashing. Note that the warranty on this car (4 years/48,000 miles) ran out of time almost a year ago, even though it was still under the mileage limit. The car has been maintained by Porsche dealers at all service intervals. So, I took it to my local Mercedes and foreign car shop in Great Falls because that's only 2 miles away (the CEL was out when I restarted the car, but came on about a mile down the road). They read the trouble codes, found that the #5 and #6 cylinders were misfiring, pulled the plugs and saw that they were carbon fouled, and thought that the coil packs were bad. Since they were only $60 each, I agreed to try that. They also replaced all the plugs ($25 each, ouch). They also found that the air filter on the left side was not correctly installed, letting air get past the filter at the bottom edge, which they then correctly installed (the filter had been changed by the Porsche dealer in my area 10 months before when I had it serviced). I drove it for a week and it started misfiring again. Back to the shop. They pulled the codes, saw #5 misfiring, and pulled all 8 plugs and saw that most of them were fouled again. At this point, they said I should take it to the Porsche dealer, so I called a tow truck and had it taken to Tysons Porsche. The dealer mechanics read the codes, found misfiring on #5, and intermittently on others, and all the plugs were carbon fouled (it had not been driven more than 100 miles since the plugs were replaced). They contacted "Porsche Tech" who advised them to try several things, including replacing the injectors. The mechanic working on my car thought that was excessive, and I agreed. If one or two cylinders had fouled plugs, I might have agreed to replace just those injectors, but all eight shouldn't be bad at the same time. No, something else was going on. The mechanic recommended doing the BG-44 treatment, including spraying into the tops of the cylinders through the spark plug holes, and he scraped the carbon off the piston tops as best he could (through the spark plug hole). He drove it and it was running normally, but still didn't seem quite right, but the service manager suggested I take the car and drive it for a week, including some spirited highway driving to clean out whatever deposits remained, and report back to him. I did that, but by the end of the week, it started misfiring again. After it started misfiring again, I pulled the spark plugs and found that #5 was not just fouled, but OIL fouled. The other plugs had more carbon than I would expect for new and recently-cleaned plugs, but not too bad. Now suspecting a major engine problem, I cleaned #5 and swapped it with another plug and continued driving it a few more days. It then started misfiring again, and again #5 was oil fouled, but this time, I pulled out my compression tester and measured the compression. I measured around 260 psi on most of the cylinders, about 250 on #6, and only 230 on #5, which was more than 10% lower than the average. Lemme repeat that: about 260 psi was the AVERAGE, which would be the result of almost 18:1 compression ratio!! That's diesel compression territory. I thought my gauge might be inaccurate, but not that far off. I went back to my local indy shop and asked the owner's advice. He was very surprised at the measured CR, so he lent me his Snap-On compression tester to measure again. With his gauge I measured an average of 275 psi! Is it possible that carbon fouling in the cylinder head/piston tops could raise the CR that high? I suppose it's possible, but extremely unusual. I then went online and searched for this problem, and found multiple references to scored cylinders and people needing engines replaced at low mileages, particularly on the Renntech Porsche forum. It appeared from that reading that some engines have a defect in the engine block casting that causes one or more cylinders to score, usually #5. Keep in mind that these are aluminum blocks and cylinders which I understand are Alusil and not rebuildable except by specialty shops. I took the car back to the Porsche dealer and told them about the unusually high compression measurements and oil fouling on #5. I suggested they do a borescope, based on the internet info I had discovered. They did so, and found scoring in the #5 cylinder. They reported that to Porsche Tech, and said they would work with Porsche to get me a new engine as a goodwill replacement. After a month of processing, Porsche agreed to provide a remanufactured engine, but it took another month and an half to get it, and then several more weeks to get it installed because the special "engine holder" was in use on another Cayenne that had its engine damaged, supposedly for a different reason. Anyway, I finally got the car back at the end of May. I had a long discussion with the service manager, whom I know from the Porsche Club around here. He said they had replaced 5 Cayenne engines that had the same problem as mine, and in those cases it was the #5 cylinder that scored. The scoring was always on 6-o'clock position of the cylinder on the left bank, which is where the piston presses when it is heading down on the power stroke. He and I discussed the likelihood that the block had a defect in manufacturing due to the molten alloy cooling too far before it fully filled the casting molds (#5 is the left front cylinder), but he didn't have any more info from Porsche than I looked up on the internet. I was thinking of keeping the old engine for parts, and also to pull the head off and see what happened in there (I'm an engineer and analyst), so I asked what the core charge on the old engine was, and he said (wait for it) $30,000!! What?!? The core charge was actually MORE than the price of the remanufactured engine, which was "only" $25,000!!! The only conclusion I can draw from this is that Porsche does not want anyone outside the factory to take apart and figure out what is wrong with these engines, and start a recall campaign or class action suit. To wind up this story, I still have unanswered questions (why the scoring, why the extremely high CR), and I guess I won't get them answered anytime soon. Even though Porsche supplied a replacement engine, and the dealer contributed something to the goodwill replacement, it still cost me $6000 out of pocket for the initial work at my local indy ($700) and at the dealer to pay for the labor to troubleshoot and then install the new engine. At least it comes with a 2-year warranty, so I guess that's worth something, but I have to say that this never should have happened in the first place. It certainly appears that there is a serious latent defect in a substantial number of these engines. Note, the Porsche V-6 and V-8 engines used in the Cayenne are also used in the Panamera sport sedan, so if you are considering any of those, caveat emptor! And, I wouldn't buy a Cayenne again, except from a Porsche dealer WITH the Porsche used car extended warranty. In fact, this experience makes me much less favorably inclined to buy any Porsche model in the future, including the 911's because they use the same technology. Too bad, because my previous experiences with Porsches of several descriptions were very positive, and I still have a 1973 911. I also should note that the Consumer Reports reliability ratings on the Cayenne that came out in January 2012 rated the Cayenne "much worse than average" in many categories, which was a substantial drop compared to the ratings in 2010 when I bought the car. Buyer beware!