Why would the gas rev up on its own on 2000 Isuzu rodeo

Is this the only time it did this? Has it done it since then? As much as people hate to admit it, the most common cause of unintended acceleration is driver error. You might simply have had your foot on the accelerator and brake at the same time. If it has done it before, or since, then you need to have the computer scanned for possible service codes. If there are none, you made to need have somebody look the engine over for an intermittent vacuum leak, or possible sticking accelerator.