I recently changed my battery in my '94 4Runner. It sat for 3 months prior due to a lack of funds to buy the new battery. Since then, it's been giving me several problems. The most urgent ones is after driving for a few minutes, the oil pressure drops almost instantly, and the temperature climbs into the red. The idle also drops from 1K to around 500rpm or less. The dipstick shows that there's no loss in actual oil though, and I just filled the radiator up with coolant.