Nissan Repair: 1988 Nissan Maxima sedan automatic, throttle position sensor, fuel pressure regulator

Question
1988 Nissan Maxima, V6 automatic, with fuel-injection.

Problem: engine starts, but dies within a few seconds.  Problem developed all of a sudden, car was working perfectly 1/2 hour earlier.
Timing belt:  I changed it at 70K, it worked fine, mileage now at 120K, I didn't check to see if it slipped a tooth.
fuel pressure normal at 30 psi (indicating pump, filter and fuel pressure regulator are all OK)
no obstruction in exhaust, I opened it in ahead of the converter
the on-board ECU computer gived a "55" signal in mode III, meaning all OK?  The ECU (electronic control system computer) is supposed to exhibit 5 self-diagnosis modes, but it displays only 4 (no mode 1).  Diagnosis mode selector displays no mode 1, it begins at mode 2.
Fuel is in the tank, removing the gas tank cap changes nothing (i.e., the air valve in the cap is OK)
spark looks good (3/8-inch) at high-tension lead to ground
rotor is where it should be, distributor cap looks good
I didn't check compression, I thought no need to since was running great just before it broke.
Oil and water normal.

Any suggestions?
Question:  If mode III ECU self-diagnosis reads "55", does this mean ECU definitly good?

Thanks for your help.

Sid

Answer
Sid,

The ECU should be fine.  I would check the air intake tract from the air meter to the throttle body to see if the airhose is cracked or the clamps are loose.  If these are good then remove and diagnose the air meter.  Get a Haynes Manual or you probably have a good manual from what you say.  Now, get a volt ohm meter and diagnose the air meter.  Other causes for starting and then cutting off could be the manifold absolute pressure sensor, the throttle position sensor or the idle air control valve.