[cardoc]

like novablue said check for vaccum leaks. hoses are les flexible and contract in colder temperatures allowing for small cracks to be become an issue. as the temps rise the hoses expand and become more flexible. if this is the problem it can be a cheap and easy fix. good luck to you

The fault code(s) stored in memory is the best place to start.

If it is getting to freezing where you are, check the vacuum hose that goes from the intake to MAP sensor for icing.

Check the front Oxygen Sensor output. It is actually an A/F sensor for fuel trim. Look to see if you can see a crack in the porceline. There was actually a recall in the States for the front O2 sensor dealing with cracking in the sensor for the automatic models.

Fuel quality: Cheap fuel with water???? High alcohol content????? Subarus don't like alcohol blends and will suffer in cold temperatures until the engine temperature is up to aid in burning the alcohol.

You might also want to check the battery and alternator. Poor amp flow will make the car run poorly.

 

[cardoc]

Hi Cardoc,

....... I ordered them from US, universal aftermarket but never had any problems since then.

I need to inspect the vacuums and will check the O2 sensor. Any advice from you on a technique to identify a bad vacuum?

You need to replace the oxygen sensors with OE fit sensors. Universal oxygen sensors never work for long. Reason being is in the manufacture of the sensor for "universal" installation. The interior pressure of the sensor is never correct and sends an incorrect reading to the computer.

See Oxygen sensor - Wikipedia, the free encyclopedia for more on Oxygen sensors.

As far as the vacuum leak check: Without a system smoker to locate leaks, your stuck with listening for a "whistle" or visually checking for cracks and loose connections on all the hoses.