1 Lucky Texan

thermal efficiency is better at higher temps, less likely to carbon-foul the plugs too. Oils are designed to be at 'proper' viscosity at specific temperatures ,etc. sure, specific engines in specific conditions might benefit from some change to operating temp. But keeping temps in the proper 'range' is best.

you must confirm the car has; proper coolant level in the radiator, not just the overflow and, correct subaru-style thermostat (with large wax capsule) I also have put small zipties to clamp the overflow tube to its nipple of the rad. neck. Puttin the front of the car up at an angle can sometimes help work air bubbles out of the coolant system. new rad cap might be a good investment too. typical HG failure will probabl;ly push coolant into, out of the overflow - may even see bubbling while idling after an overheat event. interference engine, if you are not CERTAIN the belt and particularly the idler pulleys are newer than about 100K miles OR 8-9 years, then you should do a timing belt SYSTEM overhaul.

most 'fairly modern' soobs use a 170* stat and it has a larger wax capsule (probably for the thermal mass/hysteresis) Stant's Xacstat model is probably OK too - it is built like the Subaru model.

you need the reverse-extender.

there are youtube videos showing how to use an infrared remote thermometer to measure exhaust tubing pre and post cat. If you feel the cat is working, you might try a new rear O2 sensor.

you try one of those extenders, if it prevents the code, go get your test, then continue troubleshooting. http://www.amazon.com/Blox-Racing-BXFL-00108-Eliminator-Adapter/dp/B000W1XX4M/ref=sr_1_fkmr1_1?ie=UTF8&qid=1441903416&sr=8-1-fkmr1&keywords=rear+o2+sensor+extender

first, clear the code and see if/how quickly it returns. I would never proceed too quickly on a a spurious pending code. double check for exhaust leaks - pre-cat. on a 2002, that code is not used to adjust any operating parameters. not that it may not indicate something that needs attention, just that, it's sole function is to say it thinks the cat conv. isn't working. Some people with otherwise perfectly running cars cheat the rear sensor with a resistor or an extension pipe (sparkplug extender w'ever) to avoid that code.

first - tires must be the same size/brand/model - and near each other in wear. second, automatics have a FWD fuse slot - under the hood. Put any spare fuse in there and see if the problem goes away. (I think on your car, it may be a little box on/near the right side (US pass.) strut tower?) If the problem goes away and you don't want to spend any time/$$$ on the car - you can drive in FWD mode. but, sometimes, the problem is a bad Duty C Solenoid, or, a wet clutch pack that is binding (I think some older soobs had an aluminum part that wears too quickly, there may be a steel upgraded part if you repair your trans - or you may need to install that part in a replacement trans?). some people shop for a replacement trans - often getting a used one from a junkyard with fewer miles. Some people repair their trans. any replacement trans must be the same final drive ratio. If the car is new to you, maybe a prev. owner put the wrong trans in it?

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hmmm....could be the car was restarted with the foot depressing the accelerator and it corrupted/confused the ECU's expectation for 'closed throttle' at the TPS ?? not sure it actually could be a good idea to clear the code, and re-start. Do not depress the gas pedal. The car may crank longer than typical as it will likely need to make adjustments to get to an acceptable a:f ratio and begin completing monitors.

yeah, probably a good idea to always meet strangers at the bank or in daylight at some busy area or an area under video surveillance if cash/goods will be exchanged. Perhaps bring a friend to observe if something feels 'hinky'. Trust your gut and do business in a business-like manner.

replacement trans must be the same final drive ratio. places like car-part.com or LKQ 'should' have inventory that's correct. Or maybe find someone on craigslist that is parting-out a similar model. just to be clear - all 4 tires are the same brand/model/size and near each other in wear right? critical on AWD cars.

H6 ? I see impact screwdriver recommended for all the timing cover fasteners - and make a cardboard template to store them on if re-using. start soaking them in Kroil, PB Blaster or 50:50 acetone and ATF. start that last week!

from what I've read - there is VERY LITTLE clearance on the other side of the trans pan and if it is visibly dented upwards, solenoids can be damaged, wring compromised, etc. might be an easy fix though with a new pan and solenoid set from a wrecked car.

battery cables frequently have hidden corrosion in side - under the insulation. Years of 'wicking' acid-laden moisture inside. Sometimes the cables can be felt to get hot when the trying to start. also, the 'other end of the circuit' can be part of the problem - the ground connection. many of us refresh ground connections every-time we are under the hood and spot one. There are usually some on the firewall near the pitch-stopper mount, some on the intake manifolds, usually on one or both fenders. take em loose, wire brush every connection surface fron and bacl, even the bolt. fasten them back down . I like to then smear them with dielectric grease. if the car has had lots of battery terminal corrosion in the past, or the cables get warm when starting - probably a new set of cables is called for.

was it a used or new replacement? what brand?

tranny? and rear diff ? those 2 MUST have the same final drive ratio or you will get torque bind. next time the wheel locks up, chock the other wheels and carefully jack that corner of the car up - see if the binding is released. Or, see if you can do slow, tight circles in a parking lot smoothly.

any work done or wrecks before this began? there's a very rare type of failure inside hydraulic hoses that can create a one-way valve.

so, you actually detect a vacuum when you remove the gas cap? seems like an evap hose may be clogged and, until the purge solenoid opens, you have low fuel supply. I suppose hooking a fuel pressure gauge up that you could monitor while driving might prove that theory. probably need to find the evap DRain hose. On many systems, there is a hose attached to a 2-way valve. It lets air out of the tank when fueling (or maybe when pressure builds up as gas warms?), but is supposed to let air in as fuel is used-up. probably a hose about the size of your thumb, coming from the charcoal canister area. Some cars like Mazdas attract spiders that clog evap hoses. i have heard of mud from off-roading clogging the hose. I suppose the valve could be bad......

a 5spd from a junkyard (car-part.com or LKQ ?) could be good option, but, must be the same final drive ratio as the present trans. Might find one with substantially lower miles. also, the drain plug does have a magnet. If there is more than about 1/4-1/2 teaspoon of sludge on it - or, even worse, 'chunks' - that might be a sign that a new trans is the best option.

how's the fluid level? suppose a previous owner put the wrong fluid in? make sure it has the proper level of GL-5 non-synthetic. however - it does seem like you'd have more issues than just reverse if there were a bad lube issue.

symptoms aren't a 100% match for a cap/o-ring problem but, I personally feel everyone that wants maximum reliability from a 2nd gen legacy vehicle should inspect the cap on the fuel pump assembly. http://www.ultimatesubaru.org/forum/topic/130624-2000-outback-fuel-pump-assembly-metal-cap-is-broken/

Fairtax suggested colant temp sensor - can cause good performance when cool/bad when warm with poor economy when warm - as he said - try it. Even if it doesn't help, you got new sensor and it's one less thing to suspect. there are ways to get more data; elm327 BT adaptor with a smartphone with the Torque app, a laptop with a cable and the FreeSSM program or similar, some OBD scanners can get more data. you might check this thread out; http://www.subaruoutback.org/forums/65-parts-accessories-performance/39426-freessm-complete-access-your-ecm-tcu.html

well, hope it actually helps you out! good luck!

that sucks - didn't know that. still, unit from a wreck might be the way to go. check LKQ or car-part.com . Chances are good that wrecked car started fine - might even get a starter with a lot lower miles than yours.