I was driving recently in 34 degree weather and the "red light" came on. I stopped the car and checked the oil and it looked a little thin. It ran weak and I heard a hissing comming from the rear of the engine closest to the right. I did a pressure check and got a 25psi reading whereas I was getting 150+ at the other cylinders. Could I have a burned or stuck valve? Other than taking the head completely off are there other ways to check this?</P>