One of my favorite cars, My '06 Infiniti FX45 had two intake runner butterfly screws go through the motor. I don't know when the first one went through, but the other night I was sitting at a traffic light and heard a car making a horrible knocking noise, the noise disappeared when the ford truck and I left the light, I didn't give it another thought. A couple hundred miles later I heard that horrible noise again, pulled over and could tell that it was coming from the left bank near the head - from prior experience, it sounded like something fell in the motor, but that was not very likely. I was then thinking that the CVTC cam gear or a chain tensioner was failing - as I have heard similar noises from this type of failure. I was in a bad spot and figured that even if I could drive just a mile up the road, my kids and I would be less likely to be attacked. I started driving, within a minute or so (of stop and go traffic) the engine was silent again. I drove the rest of the way home, about 50 miles, on backroads that I could easily coast off to the side if required. The noise never came back. Obviously, I knew something was wrong. I pulled the left VC off, everything looked fine. The intake came was not able to be moved freely, so at the very least, the locking pin was locked in place. I pulled the plugs, they all looked OK. I stuck the camera down the front left hole (#2) and the piston top looked ok. This engine has always had a lot of oil in the chamber and has never really had carbon deposits stick to the pistons. I compared it to pics I took a few years ago, could have been similar. #4 looked like it may have been chewing on some small stuff, or possibly detonation damage, same with #6. #8 had obviously just had a screw bouncing around in it for some period of time. The quench area on the exhaust side looks like a small mountain range. I couldn't see any damage to the intake valves or seats. I could not get a picture of the exh valves or seats (yet). That cylinder seems to have more oil in it than the others, but I think it has always been the wettest. Everything on the right side looks normal. Luckily, I never touched these screws, so at least it isn't something I did (nor is it oil related). For some background, the interior of the car is in very good condition, it is a two-tone dark brown leather and black that I like and is fairly uncommon. The body has no dings or dents. A few scrapes on the front bumper. It drives exactly the way I want it to, and it tows my trailers perfectly. I develop sentimental attachments to my cars, BTW. About 10K miles ago, as a preventative measure, I replaced the water pump and radiator (this generation of Nissan has a slight tendancy to mix ATF with coolant) and hoses. I also replaced the front lower control arms with new OE parts as the old ones were starting to make some noise. So, the car has ~185K miles on it and up to this point has had almost no mechanical failures. The A/C, Adaptive Cruise, Transmission, nothing like that. The only issues have been brakes, tires, wheel bearings, and a starter. I replaced the front driveshaft at around 140K because they are a known weak point which take out nearby parts when they fail. So, my options now are: Drive it as it is and let it eat - maybe pull back the timing a couple of degrees to make detonation less likely on my newly chewed up piston. Maybe I'll get 6 months? I wouldn't trust it. I just returned from a 3K mile trip through the mountains a few weeks ago. Get a Junkyard motor - these seem to be around $2-$2.5K for 100K engines. In general, these engines have a history of throwing rods if they are not maintained perfectly. I would figure another $1,500 for refresh parts and install help. If I could get oil pan or under valve cover pics I would be more comfortable with this. Do a partial rebuild myself - the parts for this motor are quite expensive. Just a set of OE pistons and rings and timing kit and a mix of OE and aftermarket seals/gaskets is more than the price of a junkyard engine. I would still need the machine work. That doesn't include the heads, which have titanium valves. I don't know what the service life is of Ti valves in an ideal world. If they bit on a screw once or twice... Sell it as drivable, but needs a motor and/or take it to the scavenge yard that gives me the best price. I could also sell a couple $K worth of parts, but then I would be left with a hulk of a vehicle stuck in my garage that would need to be dragged out to go to the scrapyard. My thought is that if I put $4K into it now w/ a junkyard engine, the engine might be good? The transmission will probably fail within the next 2 years, requiring replacement/rebuild. So if I set aside $10K for repairs for the next two years (about 35K miles) I paid ~$23K for this car almost 10 years ago. My replacement options are pretty much limited to the FX50 or QX70 V8 w/ the sport package and adaptive cruise/tech package in a color other than black. They are unicorns and priced appropriately. Frequently, clean low mile units that are 5+ years old will show up for $30+K a thousand miles away. Lower priced cars have over 100K miles already. My budget for a replacement car right now would be <$20K unless I finance some of it. I don't like the idea of having a car payment - at least not now. I could buy a used minivan and give up on the SUV that handles well on tight curvy roads. It's also a quandary because I don't like the way the newer cars look, but I like the way they drive. Luckily, I have an extra car that can become my DD while I figure out what to do. Logic tells me to throw in the towel on this car, I'm just afraid of getting a 100K mile 'newer' one that needs a similar amount of work and/or is less reliable. If anyone has any insight, I would appreciate it. I am also afraid that I will run into ancillary issues after pulling/replacing the motor, like A/C issues or other random stuff. I will try to attach pics of my 180K mile valvetrain and the missing screws.