Fuel System:
* Fuel pressure regulator: This is a prime suspect. A faulty regulator could be delivering too much fuel pressure to the injectors, leading to a rich mixture. Test the fuel pressure to confirm it's within specifications.
* Fuel injectors: Clogged or leaking injectors can also cause a rich condition. A fuel injector flow test is needed to diagnose this. Since it's an older car, worn injectors are very possible.
* AFM (Air Flow Meter): The AFM measures the air entering the engine. A faulty AFM will send incorrect readings to the ECU (Engine Control Unit), leading to improper fuel delivery. These are notorious for failing in these cars.
* Fuel pump: While less likely to directly cause a *rich* condition, a faulty fuel pump might be delivering inconsistent fuel pressure, which can lead to erratic running and poor mileage.
Ignition System:
* Spark plugs and wires: Worn or damaged spark plugs and wires can lead to incomplete combustion, resulting in unburnt fuel exiting the exhaust (smelling rich) and poor fuel economy. Replace them as preventative maintenance, as they are probably old.
* Ignition timing: Incorrect ignition timing can affect combustion efficiency. It needs to be checked and adjusted per the factory specifications.
Other Potential Issues:
* Vacuum leaks: Vacuum leaks can upset the air/fuel mixture, resulting in a rich condition and poor mileage. Inspect all vacuum lines for cracks or damage.
* ECU (Engine Control Unit): Although less common, a faulty ECU can cause a variety of issues, including a rich fuel mixture. This is a more difficult issue to diagnose.
* O2 sensor (if equipped): If the car has an O2 sensor (some '83 models did), a malfunctioning sensor will prevent the ECU from accurately adjusting the fuel mixture.
Troubleshooting Steps:
1. Check fuel pressure: This is the easiest and most important first step.
2. Inspect vacuum lines: Look for cracks, leaks, or loose connections.
3. Check spark plugs and wires: Inspect for wear or damage. Replace them if needed. Gap them correctly.
4. Perform a visual inspection of the AFM: Look for any obvious damage or signs of wear. These are sensitive components. A professional diagnosis is advised.
Important Note: Because you've removed the catalytic converter, the rich condition is more pronounced. The converter helped to further combust some of the unburnt fuel. This removal makes proper diagnostics even more crucial.
Recommendation:
It's best to take your RX-7 to a mechanic specializing in rotary engines. Diagnosing fuel mixture problems in these cars can be complex, and they have the specialized tools and knowledge to pinpoint the problem efficiently. A good mechanic will be able to perform the necessary tests (fuel pressure, injector flow, etc.) to accurately diagnose and repair the issue. Ignoring the problem could lead to further damage to your engine.
