Ignition System:
* Worn spark plug wires: These can cause misfires, leading to rough running (jerking), poor combustion (burnt smell – unburnt fuel), and triggering the check engine light. Worn wires can arc, causing the smell.
* Failing spark plugs: Similar to worn wires, bad spark plugs result in misfires and the same symptoms. The burnt smell could be from incomplete combustion.
* Ignition coil(s): If a coil is failing, it won't provide adequate spark to one or more cylinders, leading to misfires and the associated symptoms.
* Distributor cap and rotor (if applicable): Older models might have a distributor. Cracks or wear in these components can interrupt the spark delivery.
Transmission:
* Slipping transmission: A slipping transmission can cause jerking and a burning smell (clutch material). This is less likely to directly trigger the check engine light, but a related sensor malfunction might.
* Low transmission fluid: This would cause slipping and potential damage, possibly resulting in a burning smell.
Other Possibilities:
* Catalytic converter failure: A failing catalytic converter can overheat, causing a burning smell (often described as more sulfurous than burnt rubber). It can also affect engine performance and trigger the check engine light.
* Exhaust leak: A leak before the catalytic converter could lead to a burning smell (unburnt fuel) and potentially trigger the check engine light due to sensor readings.
* Mass Airflow Sensor (MAF) issue: A faulty MAF sensor can cause a rich or lean fuel mixture, leading to rough running and possibly a burning smell if the mixture is extremely rich. This will almost certainly trigger the check engine light.
What to do:
1. Get the diagnostic trouble codes (DTCs): The check engine light stores codes indicating the problem area. You can get this read at an auto parts store (often for free) or a mechanic. This is the most crucial first step.
2. Inspect visually: Carefully look under the hood for any obvious signs of damage, leaks, or burnt components (especially around the exhaust system and engine bay). Check the spark plug wires for cracks or damage.
3. Check fluids: Make sure your transmission fluid level is correct.
Don't delay: Driving with these symptoms could cause further damage. The burnt rubber smell is particularly concerning, suggesting something is overheating or burning. Get your car diagnosed and repaired as soon as possible.
