Gas needle goes crazy when ignition is first turned on but winds up in its proper position after a second or two,then constantly vibrates, gets louder as you accelerat. Whats the problem?
The sending unit in the tank is kaput. It has worn/dirty spots on the contacts. This is common for this vehicle. I’ve been putting up with this for a couple years now in my Silverado. The replacement unit is about $150.00 (chepaest I’ve seen off the Internet)plus the labor of dropping the tank and installing the new part.
The problem is a defective stepper motor in the instrument cluster.
GM purchased a large lot of defective stepper motors and used them in instrument clusters on their trucks. There was a “silent recall” on this item meaning the only way to get it fixed was to go to the dealer ready to pony up. They did not contact owners to let them know about the problem, or that it was their fault.
03 Silverado in my case it was the speedo.
Google “instrument cluster recall”