96 olds achieva engine miss and low coolent level

hello all just recently purchased an acheiva for my girlfriend and have been looking for some help on here and have found good suggestions! first problem I had was an engine miss i couldn`t get fix!! the fix turned out to be a used coil pack and ignitor from the junkyard $100 bucks but purrs like a kitten know! my next problem Is a low coolent level light, Ive changed the sensor on the resivor tank but no effect. any other sensors? or Ideas anyone? thanks!