* MAF Sensor (Mass Airflow Sensor): A faulty MAF sensor provides inaccurate air-fuel mixture readings to the ECU. A dirty or failing MAF sensor can cause a rich condition and rough idle. Cleaning it (carefully, following instructions for your specific sensor) is a good first step, but replacement might be needed.
* Injector Issues: One or more fuel injectors could be sticking open (constantly delivering fuel), leaking, or delivering an inconsistent spray pattern. This would lead to a rich mixture and misfires. A fuel injector flow test is necessary to diagnose this.
* Vacuum Leaks: A vacuum leak can cause erratic engine behavior, including a rough idle and rich condition. The engine might be trying to compensate for the lost air by adding more fuel. Inspect all vacuum hoses and connections for cracks, holes, or loose fittings. Pay close attention to the intake manifold gasket.
* Throttle Position Sensor (TPS): A malfunctioning TPS provides inaccurate information about throttle position to the ECU, leading to incorrect fuel delivery. This can manifest as a rough idle and rich condition.
* Ignition System: While less likely to cause a *rich* condition specifically, a weak spark from worn spark plugs, failing ignition wires, or a failing ignition coil can cause misfires, contributing to the rough idle. Inspect these components.
* Coolant Temperature Sensor (CTS): An inaccurate CTS reading can make the ECU believe the engine is colder than it is, causing it to enrich the fuel mixture unnecessarily.
* MAP Sensor (Manifold Absolute Pressure Sensor): Similar to the MAF sensor, a faulty MAP sensor provides inaccurate pressure readings to the ECU, resulting in an incorrect air/fuel mixture.
* EGR System: Problems in the Exhaust Gas Recirculation system, particularly a stuck-open EGR valve, can cause a rich condition and rough running.
Troubleshooting Steps:
1. Visual Inspection: Carefully inspect all vacuum hoses, wiring connectors, and the engine bay for any obvious problems.
2. Data Logging: If you have access to a scan tool capable of data logging, monitor parameters like short-term and long-term fuel trims, MAF readings, TPS voltage, and O2 sensor readings during idle. Deviations from normal values will point to the problem area.
3. Component Testing: Based on the data logging or visual inspection, systematically test the suspected components. This may require specialized tools or a professional mechanic.
Since you've already replaced the O2 sensors, the problem lies elsewhere in the fuel delivery or engine control system. A systematic approach using the steps above, or better yet, the assistance of a qualified mechanic familiar with Corvettes is recommended to pinpoint the issue accurately. Ignoring the problem could lead to more serious engine damage.
