[aaronh21]

Hey everyone,

new to the site here, but have been looking around at some post to see what exactly is wrong with my forester. Found some very informative points but need a little more help

Here are the detail
CAR: 2000 Forester
Miles: about 105,000
Driving: Mostly City but only a hand full of miles per week.
Location: Portland, OR
Gas Type: just regular unleaded

Problem: HORRIBLE GAS MILEAGE NOW.

Background story:
Car was acting very odd, felt like it was stalling when i would slow down, and as soon as i would speed put it felt like cylinders were miss firing, or that there was low gas in the car. They check engine light was on so i brought it in to the shop. Figured it would just be spark plugs, but they replaced the o2 sensor for PO420 . Since then, I have averaged about 120-150 miles on the tank. We were averaging around 300+ this summer.

Ideas for fixing problem:
1. New Air filter (cant remember last time it was replaced)
2. Change Spark Plugs
3. Air in tires?

I feel that if I do make this changes that I wont see THAT much a difference in my mileage. What would be my next step of action?

Cheers

 

[pleiad7]

Is the car still showing the same symptoms (running rough) since it came out of the shop? If so, the new O2 sensor obviously didn't address the problem. If it's still misfiring, check the spark plugs, wires, coilpack, and maybe the idle air control valve.

 

[aaronh21]

The problem was fixed with the jittery start but now the gas mileage is way lower than before

 

[toddlamp]

reset the ecu?

 

[funkymonkey1002]

Front O2 sensor maybe. Has the timing belt been done yet?

 

[TC2000]

felt like it was stalling when i would slow down, and as soon as i would speed put it felt like cylinders were miss firing, or that there was low gas in the car

Almost sounds like a clogged catalytic converter.

 

[wb22rules]

Running extremely rich possibly, that would contribute to O2 codes and in short order a clogged CAT and explain the rough running. The cause of that could be many things, get it to a good mechanic who would check why it threw an O2 code rather then replace the sensor and send you on your way IMO

 

[Soobs]

Running extremely rich possibly, that would contribute to O2 codes and in short order a clogged CAT and explain the rough running. The cause of that could be many things, get it to a good mechanic who would check why it threw an O2 code rather then replace the sensor and send you on your way IMO

I would take it to a Subaru dealership or a Subaru-specific aftermarket shop. I've heard of this a few times now, but the culprit can be several things.