Why would a 1991 Chevy Lumina not have any heat?

Answer 1

There are a variety of possible causes for this problem. First of all, I'd suggest checking the heater control valve and make sure that it isn't clogged and the vacuum line is connected. Also check the hoses going to and from the heater core, though usually if you've got a leak there you'll notice a loss of coolant and engine overheating problems. Same thing goes for the heater core itself. There is a door in front of the heater core itself that opens when you turn the temperature control to "heat", and this could be stuck or have a broken linkage, which is another possible cause. !

I have a 90 Lumina that wouldn't blow hot air, though the coolant system, hoses, and heater core checked good.

Dealership checked it over, including new thermostadt - couldn't figure it out.

Here's what fixed it: Reformulated gasoline reaps havoc on the EGR valve - massive carbon deposit build up. Unbolt the EGR valve from plenum, then use a dremel tool to grind the carbon buildup from both the plenum port and the EGR valve port. Use a shop vac to capture the debris as you don't want that debris getting into your plenum/valves/and lifters.

Your oxygen sensor probably took a beating too if you have a lot of carbon buildup. At $35, it's a cheap "just in case" measure.

All of that fouling likely caused your plugs to fire WAY hot, so you might want to replace them with accurately gapped platinum plugs.

Now see how hot your heater blows!

I can't improve on the answer but I can say the EGR valve has Nothing to do with the heating system of your car it Recirculates Exhaust gas so that emisions run cleaner!