90' Legacy auto:

 

Sometimes when I use the A/C the engine will stall at a intersection. Or hesitate and want to stall out. Ideas?

Check your charging system (alternator) to make sure it's still in top charging condition. Whenever you use AC, if the alternator isn't at the top condition, the AC uses a lot of power and the reduction of power (because of mediocre charging) will stall your car. Perhaps someone with a more knowledge in AC can pinpoint the exact problem but that's as far as I can guess.

Definitely sounds like a lack of juice problem here.

 

I concur that you should check the electrical charging system in the vehicle.

I know its an old school car, but my 88 GL would do that because the throttle position sensor or airflow sensor or something was going out... I forget which.

Definitely sounds like a lack of juice problem here.

 

I concur that you should check the electrical charging system in the vehicle.

Actually I think this has nothing to do with alternator or charging.

When you run your ac, the compressor clutch engages and takes power from your vehicle. You have a idle sensor that is sets the idle higher when you turn on the ac. So instead of idling at 700-800 rpm you engine will sidle around 1000-1200 rpm.

This is also why when you run your ac frequently you get lower gas mileage, the compressor for the ac take quite a bit of power to run.

I am not sure if there is a screw on 90 Subaru's but the senor could be bad or you need to turn the ac idle screw up if there is one on a 90.

three words.

Idle air control

 

check it out. the TPS does play a role in this too. as it needs to know its at idle and has increased load.