Why is there a burning smell when heat on 2001 mercury sable inside the car does idle surge sometimes on?

1. Coolant Leak: A common cause of burning smells in cars is coolant leaks. If you've noticed a sweet, almost syrupy odor and/or steam rising from the engine bay then you may have a coolant leak. Engine Coolant can come into contact with the exhaust manifold and create acrid fumes. Check the coolant reservoir frequently to keep fluids properly topped off.

2. Oil Leak: If your car is leaking oil, it can dribble onto the hot engine components and produce a burning odor. Check your oil level regularly, and get any oil leaks fixed as soon as possible.

3. Transmission Fluid Leak: Leaked transmission fluid can also get onto the hot exhaust components and produce a burning odor. Check the transmission fluid level frequently, and get any leaks fixed as soon as possible.

4. Bad Belt or Hose: If a serpentine belt or hose begins slipping, fraying, or is in any other way damaged, it can result in a burning smell. It's important to periodically check your belts and hoses for any signs of disrepair.

5. Electrical Problems: If a vehicle's wiring becomes compromised, it can lead to electrical arcing or faults. This could manifest as burning or electrical smells within the cabin.

Remember, your vehicle is equipped with a variety of sensors and should illuminate a dashboard warning light in the event of any critical system failures or malfunctions. If you notice any suspicious odors or sounds, or the "Check Engine" light is illuminated, it is best to consult a trusted mechanic as soon as possible.