After Lots of Replaced Part, Still Running Rough
Recently my 2001 Sable indicated a misfire on 2 and 6 and P1311 - Lack of Heated Oxygen Sensor Bank 1. I replaced the spark plugs and both O2 sensors. Then I was getting a misfire on 1 and 2 and the same O2 sensor fault. I detected a slight leak from the head gasket, so I ran some sealant through the cooling system and the misfires went away - car started running much smoother but not to normal. Replaced PVC and elbow, throttle position sensor, and IAC valve. Now I am getting the Oxygen Sensor Fault on Bank 1 and it fails the emission test. Check engine light is not blinking now. Any ideas on what to do next? Intake manifold cleanout, check fuel injectors, ....?