I have a '98 Outback Legacy wagon that has caused nothing but problems for the past 9 months. It will go though periods where it runs just fine and the all of sudden will run extremely rough, It happened today. I started it up at the end of the day to drive downhill on my way from work. The engine light came on and then it started to run very rough. I pulled over and continued on my way. The only problem was that I couldn't get it to go over 45 m.p.h. I pulled over, turned it off, restarted it, and it ran fine. Something similar happened a few weeks ago when I first ran the air conditioner. It completely died when I went downhill. Cleaning the battery terminals took care of this. The plugs and wires are new, gas filter replaced, along with a laundry list of other things. Oh, if my mechanic could only give me frequent flier miles, I'd be writing this from a beach in Tahiti. I'm at his shop more than the parts delivery guy!
When the engine light comes on, it comes back with an undocumented code. What's going on?