Brother, my Buick Regal was unstable after ignition in 2003, and the computer fault code was intermittent low throttle voltage. What's the problem?

Your faults are very common and generally easy to analyze. First, check whether the throttle valve and air flow sensor are clean and whether the air filter element is too dirty. If possible, you can use the on-board computer to check whether the throttle position sensor shakes when it is stationary. If so, you can try to replace this sensor.

If you do it yourself, you can borrow other cars of the same model instead.

In addition, you can see for yourself whether the pipe of the absolute pressure sensor of the intake branch pipe is installed incorrectly, which is near the throttle.

Finally, try to spend some money to repair in a reputable repair shop, because many DIY reasons are not suitable, and idle valves are very important.