Most common issues I know of with 2010-12 SHOs:
- PTU failure (as mentioned by bpd above): Expect to perform fluid exchanges on PTU and RDU immediately upon acquisition of the vehicle. A plus if the seller can provide records of a recent (within 5K miles) of such servicing. But at that mileage, I would also send a sample out for Blackstone Labs analysis to verify PTU is not breaking down. Listen for any whine/grinding when you test drive. That would NOT bode well for the PTU.
- RDU: very rarely gives way. If there is a vibration from the rear end of the car, that may be the issue.
- Driveshaft: rare, but does happen. If there is a vibration through the floorboards, that may be the center support bearings failing.
- Brakes 1: if all-OEM, performance is at best mediocre in moderate to high stress situations. At the very least, get highcarbon rotors (such as Autozone's Duralast Gold) and pair up with proven brake pads like Hawk HP/HPS, EBC YellowStuff, Carbotech Bobcats, etc. Bigggg difference.
- Brakes 2: Sometimes (not frequent at all) the booster will let go, and it will turn out that the MC has leaked into the booster. So if you run into this, replace both at the same time.
- Engine: A 1-2 second rattle at startup is pretty common, usually nearly eliminated by running the Motorcraft FL-500S filter (aftermarket filters not so good). Longer duration rattles could be timing system related.
- Engine 2: Do not skimp on oil changes, and do not use the cheapest oil you can find. This is a forced induction engine, it runs hot (and lean by design under normal conditions), and it likes being cooled properly. Oil is a big part of that (and of variable timing function).
- Engine 3: These engines do like to eat spark plugs, especially when tuned. Install fresh plugs ASAP, Motorcraft SP534's work well. They generally do not need to be regapped if installing on a stock tune engine. Usually the gap is found to be 0.030-0.035 in practice. Not worth damaging the center electrode to adjust in that case.
- Engine 4: Run top quality fuel, whether 87 or 93. Cheaper fuels will cause the fuel injectors and fuel system to gum up faster. Most fuel in the US is now E10, so if the SHO has been sitting around for any length of time, it has already been at work ...
- Transmission: Generally stout, but again, this is a pre-owned vehicle. Change out the fluid immediately. A 3x drain and fill (or a professional fluid exchange) is recommended (not a flush) as that allows you to know the condition of the trans before forcing accumulated sludge into parts that will be irreversibly damaged. Mercon LV is good enough if changed frequently enough. Watch for RPM flutter, bumps, clunks, and hard shifting under low to moderate throttle conditions. Could be signs of internal damage.
- Suspension: A few have had the rear shocks leak and fail, especially when using aftermarket springs. So if installing springs, intall new shocks & struts all around. Tie rod ends can fail sometimes. Wheel hubs/bearings DO fail, more prominently on the 2013+ though.
- Turbos 1: Check intake piping for pooling oil. That could be trouble from PCV blowby, also noticeable in the intercooler. Sometimes the intake piping will split right near the clamps (and usually on the underside of the piping), causing boost issues.
- Turbos 2: Take the intake piping off at the turbo. Pooling oil there could be a sign of leaky seals in the turbo, which could point to trouble down the road. Watch for blue smoke out the exhaust, particularly in non-WOT situations.
- Tires: See if the tires on the SHO match your expected driving conditions. Build a replacement budget for that if not. Maybe you want 2 sets of wheels/tires for summer/winter ...
- Wheels: have the wheels checked for trueness by a tire/wheel shop you trust. Bent wheels are not uncommon with alloy-type wheels. That will cause annoying vibration down the road, and wear out tires quicker.
- Water intrusion into the cabin: happens sometimes to sunroof/moonroof equipped SHOs. The usual solution is to blow out the clogged drains in that area.
- Rear sunshade motor: this can be a real annoyance as a gear will break off in the motor leaving you unable to control the shade. So check that out.
- Peeling "chrome" from taillights: a pretty common issue with the 2010s, maybe 2011-12 also. A good solution is to find replacement Taurus SEL taillight assemblies (no chrome), or possibly sand down yours and paint them, or plastidip.
- Backup camera/APIM/HVAC module: good idea to have warranty coverage for these items
Ford has extended warranty on the APIM, I believe, for now.
There are more one-off type situations, but you can search the forums to see if there is a match.
You can look over the TSBs/recalls for the SHO (i.e., taurus, look for GTDI in title) here:
http://www.revbase.com/BBBMotor/Tsb/
There are compiled lists of TSBs/recalls here also:
http://www.ecoboostperformanceforum.com/index.php/topic,496.0.html
http://www.ecoboostperformanceforum.com/index.php/topic,3836.0.html
Currently available HOW-TOs:
http://www.ecoboostperformanceforum.com/index.php/board,107.0.html
If you can, get Ford ESP warranty right away. If you can get a CPO vehicle, even better. Online ESP vendors like Lombard Ford, Flood Ford, Zeigler Ford, etc. can get you good pricing. An inspection is required if the SHO is not being sold with factory warranty. I recommend PremiumCare because it covers a LOT. More importantly, find a dealer you can trust.