My 2000 CR-V runs great at start-up, 1800 to 2000 RPM. As engine warms up and speed decreases to 1500 RPM, engine begins to miss and run rough. The missing and rough running get worse as RPM decreases toward normal idle speed. At times, engine will sputter and quit while trying to idle. OBD scan showed multiple misfires, so replaced spark plugs and plug wires. Checked timing belt and timing was perfect. New plugs and wires had no effect. Any ideas anyone?