Ok i have gone throu 5 Starters in the last month [:@]. I even put a heat shield on my 4 runner (which worked best) yet i find that it wont start after a 50 miles of constant on off moving. Since i put the heat shield on it has been doing alot better. However, my problem is that it still will not start it seems to do it when the air or radio is on, or the lights when i turn them off. then it will start but i have had a few times where that wont even work and i have to jump it i checked my battery and power connections and every thing shows full power and working i even took it to a mechanic and they checked it over and are baffled saying at first that it all leads to the starter but when i tell them that this is my 5th starter there shocked. i have suspitions that maybe my battery isn't powerful enough cause all power works but when electrical things are on it doesn't start i have 522 amp cold crank 622amp hot the battery is expired but everyone i take to says it's fine they even check the alternator to be sure and thats fine too.

Please any suggestions thank you