Nissan Repair: Z24 new engine problems, crankshaft position sensor, air flow meter

Question
My son and I just replaced the engine in our 87 4x4.  The gas was very old in the tank, and we removed most of it before starting it up and put in premium fuel.  We also replaced the fuel filter at the same time.  It ran good for about 30 miles then coming home, it will just loose all power.  Pull in the clutch and rev it up fine.  Put it back under power and it will cut in and out completely.  We got home by slipping the clutch a bit and keeping the R's up.  We performed the self diagnostic test and it makes no sence.  Once the test swich is tuned on, both led's will flash together once then twice then three times up to five and repeat.  Any help would be appreciated.  Andy

Answer
Andy,

This shows that it would be the throttle valve switch if I understand the codes that are set.  It is like Morse Code...  The following is from ask.com

Diagnostic Trouble Codes - 1987
Nissan
11   Crankshaft Position Sensor  
12   Air Flow Meter  
13   Cylinder Head Temperature Sensor  
21   Ignition Signal  
22   Fuel Pump  
23   Throttle Valve Switch  
31   Load Signal  
32   Start Signal  
41   Fuel Temperature Sensor  
44   System Okay  

Verify that diagnostic mode slesctor is turned fully counterclockwise.
Turn ignition switch ON.
Make sure inspection lamps stay on. (Bulb check.)
Ture diagnostic mode selector fully clockwise.
Make sure inspection lamps display code 23 and 31.
Depress accelerator pedal and release.
Make sure inspection lamps display code 31.
Start engine, apply brakes and shift into "D" position.
Make sure inspection lamps display code 31.
Turn a load switch OFF-ON-OFF. (A/C switch, Headlight switch etc.)
Shift into "P".
Make sure inspection lamps display code 44. Any other code is a DTC.