Auto Electronics: Oxygen Sensor, nissan d21, timing belt replacement

Question
Hello, I have an 86 Nissan D21 pickup, V6, AT, 2WD.  I recently replaced the timing belt and it ran great for a day, but as my wife tried to start it that evening it would barely run.  I checked fuel pressure, removed and checked the EGR valve, R&R cap and rotor, spark plugs, ignition timing, (it has spit up through throttle body), and checked for adequate spark.  The ECM indicates oxygen sensor, but it barely runs, I didn't think an oxygen sensor could have that much of an effect.  In desperation I tore it back down, expecting to find that the timing belt had jumped a tooth.  Nope, it is exactly where it is supposed to be.  Can an oxygen sensor create such a problem that the truck will barely run?  It is not drive-able in it's current state, I had to push it into the garage.  It will not rev over 3,000 rpm, and will not idle.  Thanks in advance, confused in Tulsa.

Answer
Kevin, while this is not exactly my specialty area, I have some ideas. First off, did it run this badly before the timing belt replacement? If not, make double sure the markings for the belt timing are correct. I can't tell you the number of times people have mistaken the correct settings. Next, make sure all wiring connections are good with no pinched or broken wires possibly caused by the work just done. I would proceed next by checking the cranking cylinder compression. If the motor is running as bad as you say, the compression should be low on all cylinders if the belt is not timed correctly. It is possible that the oxygen sensor is at the heart of the problem, driving the motor either too rich or too lean. You can verify either condition by disconnecting a vacuum line with the running engine. Note whether the newly introduced air improves the running condition (leans out the rich mixture). If not, spray some carb cleaner into the disconnected line, again noting how the engine reacts (richening the lean mixture). If in doing so, no improvement is seen, more than likely you can forget the oxygen sensor fault. One more thing to try, disconnect the exhaust in front of the catalytic converters, to make sure the system is not restricted. Good luck. Don.