How long after cars been repaired and computer cleared to wait before retesting the emissions?

There is no specific waiting period required after a car has been repaired and its computer cleared before it can be retested for emissions. However, it's generally advisable to wait a few days or drive the car for a few miles to allow the repairs to fully settle in and the engine's emissions to stabilize before conducting the emissions test. This is especially important if major repairs or changes were made to the car's emissions system.

Waiting a few days or driving a few miles allows the car's computer, known as the Engine Control Unit (ECU), to collect data and adjust its settings based on the changes or repairs made. This helps ensure that the emissions test results accurately reflect the effectiveness of the repairs and that the car meets the emissions standards.

The specific waiting period might also depend on the requirements and guidelines of the emissions testing center or jurisdiction where the car is being tested. It's best to check with the relevant authorities or the emissions testing center to confirm any waiting period or requirements before retesting the vehicle's emissions.