1. Catalytic Converters:
- Catalytic converters are essential components in a vehicle's exhaust system that help reduce harmful emissions by converting pollutants into less toxic substances. Removing the cats can impact the oxygen sensor readings, which send signals to the engine control unit (ECU).
2. Electronic Choke:
- Your 1986 GMC Sierra 2500 might have an electronic choke that relies on the oxygen sensor inputs to adjust the air-fuel mixture. Removing the cats can disrupt the electronic choke's operation, leading to potential idling and performance issues.
3. Oxygen Sensor Feedback:
- Without catalytic converters, the oxygen sensors might detect an incorrect air-fuel ratio due to the altered exhaust gas composition. This could confuse the ECU and affect its ability to make proper adjustments to the fuel mixture, resulting in driveability concerns.
4. Check Engine Light:
- The Check Engine Light (CEL) may illuminate because of the removed catalytic converters. The ECU might recognize the lack of cats and trigger the CEL to alert you to potential emission problems.
5. Emissions Testing:
- In areas where emissions testing is mandatory, removing catalytic converters can lead to failing the emissions test and potential legal issues.
To address these concerns, you can consider the following options:
- Oxygen Sensor Simulators:
Some aftermarket exhaust systems or performance shops offer oxygen sensor simulators that can trick the ECU into thinking the catalytic converters are still present, helping to avoid triggering the CEL.
- Re-tuning the ECU:
If the electronic choke is affected by the exhaust modifications, you might need to retune the ECU or install an aftermarket engine control unit that can accommodate the changes.
- Custom Tuning:
Getting your vehicle custom-tuned by a professional can help optimize the air-fuel mixture, ignition timing, and other parameters to account for the removed catalytic converters and maintain proper engine performance.
It's important to consult with a qualified mechanic or performance shop that has experience with classic GM vehicles and electronic chokes to ensure a proper installation and adjustment of your dual exhaust system while minimizing potential negative impacts on the engine's performance and functionality.
