I have a 98 lincoln navigator with a freaking boat load of problems. Heres the list of what its doing and then ill give a list of what ive done. Any and all help is seriously needed and appreciated. The truck wont idle past 600rpms and when first started bounce from 400rpms to 600rpms. It will stall out if your not on the throttle. The whole truck shakes from how hard tje engine is shaking. It has white smoke coming from the exhaust. I've never had the check engine light come on but it did through codes. First thing i did was changed plugs and coil boots. After i did that it got worse an It said both up stream heated o2 sensors heater element bad both down stream o2 sensors bad. I changed all 4 o2 sensors and cleared the codes.still no check engine light but still says all 4 are bad and now also misfire cylinder 2 and bank 2 running lean. I read up and checked the egr valve hose the pcv hose to the manifold all was good. I took the mass air flow sensor off and cleaned it with electric contact cleaner and did nothing to help. Can anyone tell me what the hell i missed and what ican do to fix this damn truck please, its driving me freaking nuts