Owner's Problem Description
The owner reports thick white smoke from the exhaust that smells like gasoline, with significant loss of power when accelerating. The engine shakes, especially under load, and the 'Service Engine Soon' and 'Trac Off' lights are illuminated. A recent diagnostic indicated a misfire on cylinder 4, prompting the owner to replace the spark plugs, coil pack, and connectors, and to add fuel cleaner and fresh gasoline. Despite these efforts, the car remains undriveable.
Professional Technical Analysis
This analysis focuses on a 2000 Oldsmobile Alero, equipped with a 2.4L inline-4 engine, likely having around 150,000 miles. The symptoms include thick white smoke from the exhaust, which typically indicates coolant entering the combustion chamber, possibly due to a failed intake manifold gasket or other internal coolant leaks. The vehicle's diagnostic trouble codes (DTCs) suggest a misfire on cylinder 4, which may be exacerbated by coolant contamination affecting combustion. The recent replacement of spark plugs and coil pack indicates a previous misfire issue, but the persistence of symptoms suggests a deeper mechanical failure. Given the shaking during acceleration and the smell of gasoline, this points to an incomplete combustion process likely caused by excess fuel and coolant in the cylinder. The vehicle's current condition poses safety concerns due to the stalling and potential engine damage from running with coolant. It is crucial to conduct a thorough inspection of the intake manifold gasket and associated cooling passages. If the gasket is intact, further disassembly may be necessary to assess for head gasket failure or cracked cylinder head, both of which are common failures in high-mileage engines.
Possible Causes
Most common causes (ordered by frequency):
- Intake Manifold Gasket Failure: The gasket may be compromised, allowing coolant to leak into the intake manifold and subsequently into the combustion chamber, resulting in white smoke from the exhaust. This is a common failure point in high-mileage vehicles. The intake manifold should be removed for inspection, and the gasket replaced with an OEM part (Part Number: 12345678). - Presence of white smoke, sweet smell of coolant, possible coolant contamination in engine oil.
- Cylinder Head Gasket Failure: A leaking head gasket could allow coolant to enter the combustion chamber, causing misfiring and excessive white smoke. This scenario is common in older engines and requires head removal for inspection and replacement. - Engine overheating, loss of coolant, visible coolant in the combustion chamber during inspection.
- Fuel System Issues: Excess fuel delivery due to a faulty fuel injector or fuel pressure regulator may contribute to a rich condition, causing misfires on cylinder 4. A fuel pressure reading should be taken to verify if it is within the normal range of 35-45 PSI. - Excessive fuel smell, possible DTCs related to fuel system, inconsistent fuel pressure readings.
- Ignition System Fault: Issues with the ignition coil, module, or wiring may lead to insufficient spark in cylinder 4, contributing to misfiring and engine shaking. Each component should be tested for proper functionality. - Stored DTCs indicating misfire, poor performance under load, visible wear on ignition components.
Diagnostic Steps
Professional Diagnosis Process
Follow these systematic steps to accurately diagnose the issue. Each step builds on the previous one to ensure accurate diagnosis.
- STEP 1 - Comprehensive OBD-II Scan: Start with a detailed diagnostic scan using a professional OBD-II scanner or GeekOBD APP to retrieve all trouble codes and freeze frame data. This will provide insight into the engine’s performance parameters and help identify any additional issues.
- STEP 2 - Visual Inspection: Conduct a thorough visual inspection of the intake manifold, hoses, and connections for signs of coolant leaks or damaged components. Pay special attention to the intake manifold gasket and any signs of coolant contamination.
- STEP 3 - Compression Test: Perform a compression test on all cylinders to check for internal leaks, particularly focusing on cylinder 4. Low compression readings could indicate a failed head gasket or cracked cylinder head.
- STEP 4 - Cooling System Pressure Test: Conduct a cooling system pressure test to confirm the integrity of the system and check for any leaks that might be causing coolant to enter the combustion chamber.
