Would the wiring harness cause your car to rum poorly?

Yes, a faulty wiring harness can cause your car to run poorly. The wiring harness connects various electrical components and systems in the vehicle, including the engine management system. If there are damaged wires or poor connections, it can lead to issues like misfiring, poor fuel economy, and erratic behavior in engine performance. In such cases, diagnosing and repairing the wiring harness is essential for restoring proper function.