Q: There is something amiss with the performance of my car, but no warnings saying what.

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I'm always driving my car, so I know when something's wrong. When I start it up it idles really rough. I've replaced a ton of stuff already. My temperature gauge is running low. My heater blows out cold semi warm air. I'm constantly sneezing inside of my car. I have replaced all the filters. I have replace the blower motor. I have replaced the idler air valve thing. I have replaced the antifreeze coolant reservoir. I have replace the idler pulley, tensioner belt pulley, and serpentine belt. I have flushed the coolant out of my car twice. But my coolant is a brown looking color. I replaced a sensor that controls the lights. Recently had an oil change done. I live in my car so I travel everywhere. I have lived in some cold areas. And I start my car at night to warm up, about 3x a night. It runs really rough. It feels like something is dragging. I've had a full tune up as well.

My car has 159529 miles.
My car has an automatic transmission.

The coolant always being brown indicates either very extensive corrosion in the cooling system, or possibly a head gasket issue. If the condition of the oil seems good (not milky or creamy), then it may just be extensive cooling system corrosion. I would try having the radiator removed and thoroughly cleaned, as well as the cooling system / engine block flushed while it’s out. Replace the thermostat at the same time. The rough running may very well be caused by a coolant temperature sensor that is not reading properly, either from being coated with corrosion, or simply an intermittent fault that is not setting the check engine light on. A certified technician can scan the system to located the cause of the rough running and inspect the cooling system.

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