The Chevy Cavalier does have a fresh air intake filter. The fresh air intake filter is located behind the passenger side kick plate.
Possibly some leaves have entered through the fresh air intake.
The air filter on a Honda Odyssey is located next to the air intake. It filters fresh air which comes in from the front of the engine compartment.
The air intake is positioned so it can pull fresh air from the grille. This opening should be well below the location of the actual air filter so water should not be a big issue, but there are fresh air kits available to get the intake even higher.
Sounds like you may have dropped something down inside of one of the heads when you had the intake off. Is it full of fresh clean oil and a new filter????
Usually at the fresh air intake at the bottom of windshield passenger side (open hood)
If the fresh air intake has a filter, you can change it as necessary. I would imagine once a year would enough.
Most likely this is the "Fresh Air Intake" door malfunctioning; rear AC's normally do not have the ability to draw fresh air, and normal AC system have fresh air intake that draws hot air from outside.
compressor maybe sticking which doesn't filter freon through the system
The intake for the HVAC system is under the cowl panel behind the engine on the passenger side. The cabin air filter is also there and can be accessed by removing the snap on cover on that side.
How do I check or change my filter on my fresh water well?
The difference between a fresh air and a regular intake on a vehicle is the location of the inlet. Fresh air uses and inlet at the extreme front of the vehicle, while a regular intake can be anywhere and pull in heated air from the engine.
To replace the thermostat on a 91 Cavalier you need to drain the radiator. Remove the top radiator hose and water inlet. Remove the thermostat from under the inlet. Install the new thermostat and reinstall the inlet and hose. Fill the radiator with fresh antifreeze.