I would disregard most sensors like the o2-by default the ecm will run the car just fine even if they are all bad-the sensors just "fine tune" it all for economy and emissions. Without a real good code reader (one that can turn off things like egr, purge valve, etc) i would first unplug the o2 sensors, egr, etc(pull it off and make sure its closed), drive the car and see if you get any change for the better. If yes, plug 1 sensor in at a time-clear codes, drive, repeat this process until the bucking issue starts-that will show you the bad (if any) sensor.
Another thing to look at is the valves. Are they within adjustment, is the vtech valve bleeding psi and engaging just a few valves (when they should be off)
Another thing to try is shut off the ima via switch. My car was bucking real bad, I had thought it was the egr, I went through everything, sensors, egr, cats, fuel system, only to find that the "new" bcm i had didnt play nice with my original ecm and mcm( my ecm is a first version, no re-flash, mcm is a # 10) It was causing the ima to kick on and off fast without showing it on the dash at certain speeds.
(oh, as for if a cat can be bad at 100k, yes, mine seem to last about that long and then i get codes. Ive replaced 2 on mine so far, and have the code now-just in time for 300k. But im going to try cleaning it this time lol)
Last edited by biododge1; 11-15-2012 at 02:39 AM.