I’ve got a 02 Outback that sat for 5 years with 50% full tank. I had to replace the timing belt and head gaskets. Being an idiot I didn’t drain the fuel tank and left the fuel in it. I put a fuel enzyme treatment and a high quality fuel system cleaner with 5 gallons of new gas. its giving a code for the h02 sensor circuit being low and occasionally cylinder 2 and 4 misfire. I’m guessing it’s the old fuel giving these codes. The thing that confuses me though is that I only get cylinder 2 and 4 giving the misfire and not 1 or 3. Could it be timing?
Bank 1 sensor 1 gives 1.3v and sensor 2 give 0.1. It’s Ltft is -20% and stft is all over the place
Update. Did a vacuum test and the gauge fluctuates between 10-15 inhg rapidly. What are your ideas? I’m thinking maybe I need to adjust the valves? Could it be spark plug wires? Timing? Still have a ltft of -18% and a stft of 0.8-0 when idling
Take it out on the highway a really blow it out. Then check the codes.
That’s my plan
Just don’t pull off a Hyundai/Kia
Had and fixed an exhaust leak and went through the tank of gas. Just put in some cata clean because both codes are still present. I’m thinking it may be clogged. From the way it smelled when I put it in to the tank I’m thinking I’m going to see some smoke while I’m going down the highway
The fuel tank's most likely plastic, if so, there's not a huge chance of rust or something like that clogging up your fuel filter. If the tank's for sure plastic, you might try to just drive out as much of that old gas as you can and add new gas every half to quarter tank. That will dilute and flush out the old fuel that's still there.
When I resurrected my '79 Catalina after 5 years of sitting, I didn't drain the carb or gas tank like you. It started and ran on the old gas, not the greatest, but it did. I ran it at home after putting 5 gallons of new gas in as well. Once I got it driveable again, Putting a couple full tanks of gas cleaned out all of that old nasty fuel and it starts right up now.
Sea-Foam it?
I no longer use sea foam. It never helped as much as the stronger cleaners. I double checked the code and realized it was for the heating coil circuit not the sensor circuit. Checked the sensor plug and one of the wires had popped out. Put it back in and now the code is gone. However it’s still pretty shaky at idle in neutral/park. I’ve ran the tank to empty before I filled up the tank so there shouldn’t be much bad gas to cause it. Plus it misfires only on cold starts. Could it be the spark plugs have carbonation on them? They’re pretty new but I wonder if the bad gas gunned them up. Also it only misfires on cylinder 2 and 4 which are on the same head but never 1 or 3 which are on the other head
Just remembered that subarus with this engine generation had problems with the rubber hosing that connects the fuel rail to the fuel lines. It would shrink in the cold and allow fuel to leak then would dxx C pans and seal back up. I’m going to check the hose tomorrow