No heat, erratic idle

[Eastwood95]

Ok, I live in New York and today was the coldest day in the last two years. I go start my car to warm it up before work. Turn the heat on full blast and go inside. The idle was high, as usual before it gets to normal operating temps. But, as about 10-15 minutes goes by, I didn't hear the idle dropping. I close my door to head outside and the idle starts to go up and down by itself, kinda like a vacuum leak or something. I get in the car, and there is no heat whatsoever, and the idle keeps rising and falling. I drive the car down the street and turn around, and the idle finally settles, but there is still no heat.

I didn't have time to pop the hood or look at anything when I got to work because I was barely on time. I did a quick search and got a few ideas about how to check the heat, but I'm still not sure because I've never had to deal with the heating system. I was wondering if there was a link between the erratic idle and no heat, or if I have two separate problems.

Any ideas?

Edit: I go start my car for lunch, heat is working. It was still intermittent at first. I revved it up a little to help warm it up, and when i let off the throttle, the heat went away. I revved it again and it came back on. Then I let off, and it stayed on.

 

[luv2rallye]

No heat can be radiator coolant level not full, stuck thermostat, heat door not opening. Your erratic idle problem is not related - check first for vacuum leaks as you said. Leaking hoses or intake gaskets. Spraying suspect intake gasket with WD40 which then causes rpm drop is sure sign. If not that next check the throttle position sensor.

 

[xveganxcowboyx]

Mine has done this on really cold days when my coolant is mixed too weak. I think what happens in the coolant freezes in the heater core, which causes loss of heat. I believe the TB lines also freeze which messes with the idle speed controller or some other gizmo I don't fully understand. When the temp goes back up or after some driving it should clear up.

Of course I don't know if this is your problem. The heat has never been eratic for me. It doesn't work, then it unthaws and works. It's possable there were chunks of ice blocking the passages for a while.

 

[Eastwood95]

Its still acting funny. It seems like when I rev the car, or if i'm cruising the heat works fine. When I let off the gas, or I'm at idle, the temperature of the air coming out gets cold. I'll check my coolant mix....

By the way, the idle problem hasn't occured again......yet

 

[Irrational]

I would through a new thermostat in there and see what happens.

 

[Turboeagletalon]

i had the same problem you did. i get the rpms' above 3500 and the heat works. but mine over heats at idle