My car(90' olds eighty eight royale) is making a hissing sound when the engine is turned on. It sounds like it is coming from the general area of the back spark plugs. When i turn the engine off it hisses and then dies down within about 2 seconds. We just replaced the spark plugs but my grandpaw kinda laid on the engine while puttinb the pesky back plugs in. Dont you think that if it was a spark plug the engine would knock hard?? That what my mom says but i still think it could be a plug that was forgotten to be tightened.
I donno what do you think??