High Hydrocarbons (HC) & Check Engine Light:
* EGR Valve (Exhaust Gas Recirculation): A faulty EGR valve can cause high hydrocarbon emissions. It recirculates exhaust gas back into the engine to reduce NOx emissions, but if it's malfunctioning, it can lead to incomplete combustion and high HC. This often triggers a check engine light.
* PCV Valve (Positive Crankcase Ventilation): A clogged or faulty PCV valve allows crankcase pressure to build up, leading to leaks of unburnt hydrocarbons into the intake system and contributing to high emissions. Again, this often triggers a check engine light.
* Oxygen Sensor(s): These sensors monitor the oxygen levels in the exhaust. A failing oxygen sensor can cause the engine to run rich (too much fuel), resulting in high HC emissions. This usually sets a check engine light.
* Mass Airflow Sensor (MAF): The MAF sensor measures the amount of air entering the engine. A malfunctioning MAF sensor can cause the engine to run rich or lean, leading to high HC and triggering the check engine light.
* Fuel Injectors: Leaky or clogged fuel injectors can lead to incomplete combustion and high HC.
* Spark Plugs/Ignition System: Worn spark plugs or other ignition system problems (wires, coil packs) can result in misfires, incomplete combustion, and high HC.
Water Leak on Passenger Side:
* Leaking Heater Core: This is a common source of leaks on the passenger side. A leaking heater core will leak coolant (which is often mistaken for just water) into the passenger compartment. This is a serious issue that needs immediate attention.
* Sunroof Drain: Clogged sunroof drains can overflow and cause water to leak inside.
* A/C Condenser: While less common, a leak in the A/C condenser can cause water to drip inside the passenger compartment.
* Seal Failure (Window, Door): A leak in a window or door seal.
Connecting the Dots:
The water leak is likely unrelated to the emissions problem, but it's important to fix it regardless. However, some of the problems causing high HC emissions *could* also be contributing to the check engine light. The check engine light will give a diagnostic trouble code (DTC) which can help a mechanic pinpoint the problem quickly.
What to Do:
1. Get the check engine light diagnosed: A mechanic can read the diagnostic trouble codes (DTCs) to identify the specific problem(s) the computer has detected.
2. Address the water leak: Locate the source of the leak. This will likely require a mechanic’s expertise.
3. Emissions Retest: After addressing the likely causes identified through the diagnostic codes and repair, have your vehicle retested.
Ignoring these issues could lead to more serious damage to your engine. It's best to have a qualified mechanic diagnose and repair these problems as soon as possible.
