Here's why:
* Engine Management System: The fuel-injected 1990 Caprice relies on a sophisticated engine control module (ECM) and various sensors to manage fuel delivery, ignition timing, and other critical functions. A carburetor lacks this electronic control. You'd need to completely remove the fuel injection system, including the fuel rails, injectors, sensors, wiring harness, and the ECM itself.
* Intake Manifold: The intake manifold designed for fuel injection is completely different from a manifold designed for a carburetor. You'd need a new intake manifold compatible with a carburetor. Finding one for a TBI (Throttle Body Injection) engine might be possible, but it might still require considerable modifications.
* Fuel Pump and Lines: The fuel pump and fuel lines are designed for the pressure and flow requirements of fuel injection. A carburetor system needs a different pump and potentially different fuel lines.
* Vacuum System: The vacuum system on a fuel-injected engine is much more complex and supports various functions controlled by the ECM. A carburetor system uses vacuum differently.
* Ignition System: While the ignition system itself might not need complete replacement, adjustments would likely be necessary to accommodate the change in fuel delivery.
* Emissions: Converting to a carburetor would almost certainly make the vehicle fail emissions testing in most jurisdictions. Carbureted engines generally produce significantly more emissions than fuel-injected engines.
* Complexity and Cost: The project would be incredibly complex and labor-intensive, requiring significant mechanical expertise. The cost of parts and labor would likely far exceed the value of the vehicle.
In short, while theoretically *possible*, converting a fuel-injected 1990 Caprice Classic to carburetor is impractical, expensive, and likely illegal in most areas due to emissions regulations. It's far more cost-effective and sensible to repair or replace the existing fuel injection system if it's malfunctioning.
