Hello from a newbie. Got a 2000 Tundra, 4.7 V8. Yesterday I tried to start my truck but the battery seemed drained. Notice the Cap was loose on top so I added some distilled water and recapped. Was hard to jump start, but got it going. Idles so low now that I can only keep it going except by pumping the accelerator. Will continue to run as long as I press the gas, but quickly dies if I dont. Is this a result from a bad battery alone or is there possibly something else going on?