90 psi is too low for the engine. What are the other cylinder readings?
The cost would depend on what needs to be done and without taking the cylinder head off, it is not possible to provide any estimates. If only valves are causing the problem it would be cheaper but still should be more than $ 1,000 for a start.
Problem can only get worse and with continued driving, you are definitely going to damage the catalytic converter if it is not already damaged.
Monday, October 15th, 2012 AT 6:57 PM