Most of the time this kind of stuff isn't a big deal and it just needs proper diagnosis and maintenance.
A friend outside philly was told she needed a new engine (basically same engine as yours in a legacy sedan) due to cylinder misfires (some of the same codes you have), I talked to the shop and they said they tested and it's not worth fixing. but they didn't do any real diagnosis, I told her to drive it to me and I fixed it for like $100 with new plugs and wires.
***How is it running? Good or terrible?
First 4 codes indicate all 4 cylinders - so this should be (with the limited info you've given) something that affects all 4 cylinders, which are:
1. Clear the codes and see which ones come back first - read them the moment the light comes back on or even check before the light comes on for pending codes. Which ones come back first?
2. Check the charging system. Alternator, battery, connections. Poor elecrical system will result in phantom codes.
NAPA, Autozone, Advance and others do on car testing for free. Drive in and let them test it if you can't.
3. verify the crank pulley isn't separating (draw a line across the face of the pulley and check it a couple times the following weak to see if the line is "broken").
4. Has the timing belt or pulleys ever been replaced? It's an interference engine so if any of those fail you'll have a non running blown engine and $$$$ repair.
his is unlikely if the car is running fine.
5. test or swap in a used ($30) coil pack. they're a dime a dozen, i probably have one and have thrown them away.
ebay, www.car-part.com for used ones cheap.
The following are less likely since we're talking about all 4 cylinders (although I should know how long those codes have been there, which come back and how fast - but I have to guess with the limited info you've given) - so these aren't likely but they are the most common cause of some of those codes you have if they showed up by themselves.
6. They need Subaru or NGK or other high quality premium wires and NGK stock plugs. I've seen brand new wires cause misfires on those engines (more so on those engines than others) from day 1. But I wouldn't expect all 4 to be bad at the same time, so that's why I say it's unlikely based on some assumptions.
7. pull the plugs and check for oil on them - the valve cover spark plug tube gaskets leak and get the plugs wet. most by this age/mileage have needed replaced already, i've done tons.
Have those spark plug tube gaskets ever been replaced?
Thanks so much, Grossgary!
The car runs fine--with one, possibly revealing exception: after driving for a few miles/getting warmed up, it occasionally "lurches" (misfires?). I'll be going along at 55-60 mph and the engine will quickly lose and gain power again. There is, rarely, a backfire. Minus the backfire it feels almost like when I was first learning to drive stick and messed up the timing; speaking of which, this is a manual transmission, if that is helpful to know. It's been doing the lurch for a loooong time, which was why my husband replaced the plugs last summer (NGK's). Thad didn't make the lurching stop, though.
The timing belt was replaced, as were the head gaskets, before we got the car, but we don't know if the pulleys were replaced with the timing belt.
This all came to a head about a month ago, when I started out one morning and, suddenly, the lurching and backfiring were happening non-stop. At that point, my husband cleaned the MAP sensor. Then, it was drivable again, with much less frequent lurching and no backfiring. After this, I noticed a reduction in power when there's a load on the engine, going uphill for example. Right now, I'm not driving the car much for fear of getting stranded in the middle of nowhere--I'm a free-lance musician and drive a lot of long distances.
Other hints of something amiss: the temperature gauge sometimes plummets when it's cold outside--doesn't have to be unusually cold, and, when it plummets, the heat coming out of the vents becomes lukewarm. Coolant level is fine.
You asked about electrical: No issues, except that the fog lights both stopped working. We replaced one bulb, which didn't fix it, and used at multimeter to discover that no power is getting to the fogs....Maybe simply a wire somewhere, but thought I'd mention it, just in case.
We have never replaced the spark plug tube gaskets. In light of the fact that the lurching is intermittent, is the coil swapping idea worth trying?
Our point in taking "Fred" to the dealer (which is the only place that works on Subies up here in the armpit of western PA--about an hour north of Pgh.) was to diagnose so we knew what needed to be fixed. My husband has been a service writer for Nissan and is very familiar with motorcycle engines, and has done a lot of the repairs on our cars, himself. We don't know where to begin with "Fred", however, and the dealer apparently doesn't need our business.
I hope I've given you more info to go on, and I really appreciate all your advice. Thanks, again!