Patent ID: 7930087

Claim:
A method of operating an engine having at least one cylinder and an intake manifold for directing air to the cylinder, comprising: discontinuing combustion in the cylinder for at least one cycle by temporarily halting delivery of fuel to the cylinder; during a first condition after combustion is discontinued, operating the cylinder to provide at least one of compression braking and expansion braking by holding one of an intake valve and an exhaust valve closed while opening, closing, and opening the other of said intake valve and said exhaust valve; during a second condition after combustion is discontinued, wherein said second condition includes a request to increase the vacuum level within the intake manifold, varying an operation of at least one of the intake valve and the exhaust valve to increase air flow through the cylinder, and subsequently varying an operation of at least one of the intake valve and the exhaust valve to reduce air flow through the cylinder when the request is satisfied; and resuming combustion in the cylinder by re-initiating delivery of fuel to the cylinder, wherein the amount of fuel delivered to the cylinder during a number of cycles after resuming combustion is based on an amount of oxygen provided to the exhaust during said discontinued combustion operation.