95' Legacy P0170 & P0120 Codes

[kimkathan]

I have a 1995 Legacy 2.2 176,000 miles. The other day the CEL came on and codes P0170 (Fuel Trim Malfunction Bank 1) and P0120 (Throttle Position Sensor/Pedel Position Sensor A Circuit Malfunction) both came up.

 

The fuel consumption of this vehicle has been slowly decreasing over the past few weeks (from 26mpg down to around 20mpg now) the fuel guage has also gone a bit screwy (says its on E at 180 miles, light has not come on yet though)

 

Other than the fuel consumption droping and the CEL coming on there is no problems as of yet with the way the car is running.

 

Any advice on where I should start?

 

I've looked back at some searches for the codes I'm going to check for exhaust leaks today, but from there, I'm still a bit lost as to where to go from there as to which sensors to check/replace.

[Legacy777]

First thing I'd recommend is clearing the codes, driving the car and seeing if the same codes come back.

 

Regarding the fuel level/gauge. Either the sender or wiring is acting up, or your mileage is really bad.

[kimkathan]

OK, I cleared out all codes. Drove the car for the last 2 days and did fine til coming home tonight, CEL came on, checked codes and it was only the P1070 came up (Fuel Trim Malfunction Bank 1)

I did check for leaks and didn't find any. In the past (6-8 months ago) I did get a code for O2 Sensor Bank one that came up, cleared it out, and it never has come back (thought that probably it was related to moisture somehow getting in the connection).

 

Any advice on where to go from here?

[Legacy777]

Well....I'm not really sure what would cause a fuel trim error code on one bank.

 

You could try running some seafoam through the fuel system.

 

Anybody else have any ideas?

[ferret]

Bank 1 on a Subaru means the entire fuel system since there is only 1 pair of Oxygen sensors. Unlike a V6 or V8 which may have a bank 1 on one side and bank 2 on the other.

 

In any case Fuel Trim Malfunction can be an exhaust leak, intake leak, fuel pressure......Anything where the fuel feedback system can NOT compensate for an incorrect air/fuel ratio.

P0170.pdf

[idosubaru]

at 176,000 miles i wonder if a fuel injector could be the issue? i had mine cleaned professionally off the car (remove them, ship them to a company who rebuilds them, reinstall). some tested as "leaking" or "dripping" and i've seen others tested the same way on some other board members vehicles. this was somewhere around 150,000-200,000 miles, i can't really remember. seems to me it was closer to 150,000.