Impreza Outback / 99 / 110,000 mi / manual / everything stock
First the car started jerking (due to misfire I guess) when accelerating, especially pronounced at the at low RPMs of 2-nd and 3-rd gear. Nothing weird on idle or rev-ing the engine without load. No lack of power when it goes above 3000 RPM on the highway etc. In a couple of days I almost learned how to accelerate carefully with a bit more gas after each shift so you almost can't feel it.
Then the CEL turned on. Checked the code - P1130 - "Front oxygen sensor circuit malfunction (open circuit)". Reset the error code and in a while the generic P0302 - "Cylinder 2 Misfire Detected" appeared (no P1130 though).
Searched the web and found a couple of postings where this combination of symptoms - misfire/P1130 was due to bad fuel pump. Tried to compare which one is harder - to change the pump or the sensor and the sensor behind all those rusty bolts and under the car looked the worse one.
So changed the fuel pump and fuel filter. And nothing changed. Well may be the jerking a little bit and with the new pump the CEL never came off (guess some better fuel flow helped a bit).
Next thing, changed the O2 sensor. The store had the universal (and cheaper) one in stock. Read the warnings about the universal sensors but this was BOSCH and looked OK. The problem with it was that it had three wires while the OEM had four. The booklet has a conversion table and they claim the missing wire is the common so OK I'll buy that.
With the new sensor though I immediately get P1133 - "HO2S insufficient switching" and whenever I turn it off with the scanner it comes again in a couple of seconds. The misfire is much worse.
Any ideas? I know I messed up with the new sensor (as if the old one was good) not sure how though. There is a slight chance the new sensor was bad but this -
Any help is highly appreciated...