Hello everyone I have a 1992 subaru legacy 2.2 fwd. I have noticed lately that the heat goes in and out. It generally works really well when driving 40 mph+ but blows cold when going slow or idling. Though sometimes it runs fine all day. My blower fan is going but I'm not sure if there related. Also when I'm in gear and I don't hit the gas it tries starts to stall and bounces back up and then tries stalling again but no issues while driving. If anyone could help that would be great.

 

Thanks

HAS

Start with the basics. 

Check the radiator level when cold at the radiator

Is the over flow tank full and does the engine suck coolant back into the engine when it cools down

When is the last time the timing belt, pulleys and water pump was changed

Where does the temp gauge sit when hot and is it always at the same spot

 

You will most likely find the answer.

The radiator is full but the overflow tank is empty and the temp gauge always stays just below the halfway mark. The timing belt, pulleys and water pump were changed about 18k ago. There are no visible leaks from the hoses or anywhere else that I can see. I forgot to mention the lower the fan setting the hotter the air it blows.

How old is the thermostat and radiator cap.

 

When was the last time it had a tune-up?

As far as I know they are original to the car at least I don't have any records of them being changed. The last tune up was 10 years and 90k ago but I did the plugs a couple months ago because it was stalling really bad it went away after I did them but now it does it while idling in gear

Full tuneup time including PCV valave. Gte a base line. Fuel filter too

Thanks I will do that but I don't think that will help with the heat going in and out. I'm not sure how to troubleshoot the heat

Thanks I will do that but I don't think that will help with the heat going in and out. I'm not sure how to troubleshoot the heat

 

Heater door actuator?

No but it may help with surging and wanting to stall.

 

You described two issues not one.

 

But let me ask you this, when you check your plugs do they look TOO clean. If you have coolant leaking into the intake manifold that could fit some of the issues your having.

Are these vacum actuated doors?