* Injectors: Clogged or leaking fuel injectors are a prime suspect. Clogged injectors prevent the proper amount of fuel from being sprayed into the combustion chamber, leading to a lean mixture (not enough fuel) in some cylinders and a rich mixture (too much fuel) in others. Leaking injectors constantly drip fuel into the cylinders, resulting in a rich mixture. This unburnt fuel exits through the exhaust as raw gas.
* Fuel Pressure Regulator: A faulty fuel pressure regulator can either fail to maintain the correct fuel pressure or allow fuel to leak back into the return line. Low pressure leads to a lean condition, while high pressure or leakage contributes to a rich condition. A rich condition, again, leads to unburnt fuel in the exhaust.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. If it's faulty and reporting incorrect air flow, the computer (PCM) will adjust the fuel mixture incorrectly, potentially leading to a rich condition.
* Oxygen Sensors (O2 Sensors): These sensors monitor the oxygen content in the exhaust and help the PCM adjust the fuel mixture. Faulty O2 sensors can provide inaccurate data, causing the PCM to deliver too much fuel.
* Throttle Position Sensor (TPS): A faulty TPS might provide incorrect information about the throttle position, leading to inaccurate fuel delivery calculations by the PCM.
* PCM (Powertrain Control Module): While less common, a faulty PCM can mismanage fuel delivery. This is usually diagnosed after other components have been ruled out.
* Vacuum Leaks: A leak in the intake manifold or vacuum lines can disrupt the air/fuel mixture, leading to inefficient combustion and raw fuel in the exhaust.
* Fuel Pump: While less likely to cause *raw* gas fumes, a weak fuel pump might not deliver enough pressure, creating a lean condition and potentially leading to some unburnt fuel. However, a weak pump would mainly present as lack of power and stalling.
Troubleshooting Steps:
1. Check for Diagnostic Trouble Codes (DTCs): Use an OBD-II scanner to read any error codes stored in the PCM. These codes can point directly to the faulty component.
2. Fuel Pressure Test: A mechanic can test the fuel pressure to ensure it's within the manufacturer's specifications.
3. Visual Inspection: Inspect fuel lines and injectors for leaks. Look for signs of fuel dripping or spraying.
4. Exhaust Gas Analyzer: A mechanic can use an exhaust gas analyzer to measure the composition of your exhaust gases. High levels of hydrocarbons (HC) indicate unburnt fuel.
5. Component Testing: Individual components like the MAF sensor, O2 sensors, TPS, and fuel injectors can be tested with a multimeter or specialized diagnostic tools.
It's crucial to have a qualified mechanic diagnose the problem. Trying to fix this yourself without proper tools and knowledge could lead to further damage or injury. The combination of raw gas fumes and excessive fuel consumption indicates a serious issue that needs professional attention.
