Code Diagnosis on Legacy Outback 2.5L

[Sparky19]

This 1995 outback is throwing a P0130 and P0170 codes and getting bad
fuel economy. The car runs just fine otherwise. I had the O2 sensors
replaced (twice) and still the same problems. New plugs, air filter,
etc. Now what?

P0130 = Oxygen Circuit Malfunction
P0170 = Fuel Trim, Bank1 Malfunction

Thanks much!

 

[AS]

Check for ignition problems, defective Crankshaft, camshaft position
sensor, maybe defective cat

 

[Carl 1 Lucky Texan]

This 1995 outback is throwing a P0130 and P0170 codes and getting bad
fuel economy. The car runs just fine otherwise. I had the O2 sensors
replaced (twice) and still the same problems. New plugs, air filter,
etc. Now what?

P0130 = Oxygen Circuit Malfunction
P0170 = Fuel Trim, Bank1 Malfunction

Thanks much!

The 130 seems to be FRONT O2 specifically.
I've read many times of folks having problems with aftermarket sensors.
Maybe an OEM sensor should be installed if it wasn't. I think better
shops have ways to scope/test the sensors to make sure they aren't
'lazy' and are in the proper range. There are some tests also for cat.
converters. Many things can cause a fuel trim issue. MAF, IACV, bad
injector, maybe even the engine temp sensor (not the temp gauge sensor).
Your car needs proper diagnosis before throwing more guess work at it.

Carl

 

[Sparky19]

The 130 seems to be FRONT O2 specifically.
I've read many times of folks having problems with aftermarket sensors.
Maybe an OEM sensor should be installed if it wasn't. I think better
shops have ways to scope/test the sensors to make sure they aren't
'lazy' and are in the proper range. There are some tests also for cat.
converters. Many things can cause a fuel trim issue. MAF, IACV, bad
injector, maybe even the engine temp sensor (not the temp gauge sensor).
Your car needs proper diagnosis before throwing more guess work at it.

Carl

Thanks for the replies. I'm digging deeper into all the other
components now. MAF first, then other components, maily the ignition.
But I thought a bad injector would throw a separate code? And
Ignition component malfunctions would make the car run badly. It runs
great except for fuel consumption.

Sean

 

[Carl 1 Lucky Texan]

Thanks for the replies. I'm digging deeper into all the other
components now. MAF first, then other components, maily the ignition.
But I thought a bad injector would throw a separate code? And
Ignition component malfunctions would make the car run badly. It runs
great except for fuel consumption.

Sean

The Engine Temp sensor is famous for going bad with no 'direct' code
pointing to it. And it often has very subtle symptoms except for poor
mileage (basically, it can fail such that the ECU thinks the engine is
always cold - forcing a 'choke' condition all the time instead of during
warm-up only) If the car runs well, it may not be the MAF (yay!) as it
will often cause stalling and rough running. IACV might also cause rough
idling. Sometimes bad converters cause 'bogging' especially at highway
speeds/under load and warmed up. The rear O2 sensor usually has a longer
life that the front one and the code seems to point to the front
anyway.....dunno
I suppose the ECU could be bad.
I would be very tempted to change the Eng. Temp sensor if I couldn't
find a good soob mechanic to diagnose it for me. (on most soobs, it is
next to the temp. gauge sensor but may have 3 wires? IIRC?)

good luck and let us know what you discover.

Carl
1 Lucky Texan