91 buick regal custom 3.1 engine had minor tune up now it runs rough and stalls after warms i ran a code search came with 0.pos. trottle position sensor or fuel injection cat.converter?

The trouble code 0.pos. (zero position) on a 1991 Buick Regal Custom with a 3.1 liter engine usually indicates an issue with the throttle position sensor (TPS). The TPS continuously measures the position of the throttle valve, which is used by the engine control module (ECM) to determine how much air is flowing into the engine and to calculate the fuel injection pulse width. If the TPS is faulty, it can send incorrect signals to the ECM, resulting in a rough idle, stalling, and other performance issues.

Here are a few things you can check to troubleshoot the TPS:

1. Electrical connections: Check the wiring harness connector to the TPS for any loose or damaged connections. Make sure the connector is properly seated and that there is no corrosion or damage to the pins.

2. TPS sensor: Inspect the TPS sensor itself for any signs of damage or wear. Look for any cracks or broken components, and check the condition of the sensor's shaft and lever arm.

3. Throttle body: Check the throttle body for any dirt, debris, or obstructions that could prevent it from closing properly. Clean the throttle body and inspect the throttle plate for any damage or wear.

If you do not find any obvious issues with the TPS or the throttle body, you may need to use a multimeter to test the TPS sensor's resistance and voltage output. The specific test procedure will vary depending on your vehicle model, so you should refer to a reliable source of repair information for your specific vehicle.

If the TPS is found to be faulty, it will need to be replaced. It is important to use a high-quality replacement TPS to ensure proper engine performance and reliability.