You have a valve problem. A more-involved cylinder leakage test will identify the cause of the low compression. You may find a tester at an auto parts store that rents or borrows tools. Compressed air is injected through the tester, then you listen for where it's leaking out. For a hiss at the tail pipe, it's a leaking exhaust valve. A leaking intake valve will be heard at the throttle body / air filter box. Leaking piston rings will be heard at the oil cap or dipstick tube. Bubbles in the coolant reservoir indicates a leaking head gasket. If there is no excessive leakage, suspect a broken rocker arm that is preventing one of the valves from opening.
Please consider a to help us answer more questions.
Tuesday, February 12th, 2013 AT 1:45 AM