A method for performing an acid stimulation operation using a downhole tool includes conveying the downhole tool in a borehole that is formed in a subsurface formation. The downhole tool includes a chamber to store stimulation fluid comprising a stimulation acid. The downhole tool includes a fluid injector that is fluidly coupled to an output of the chamber via a flow line of the downhole tool. The method includes coating the flow line with an acid resistant fluid. The method includes injecting, from the fluid injector via the flow line, the stimulation fluid into the subsurface formation that is released through the output of the chamber.