So we replaced the engine in a 1992 Sentra with one from a junkyard.
The actual process of putting the engine in went without a hitch, the only problem now is that it doesn't run correctly.
To be exact, it WILL start, and sound great for maybe 1 or 2 seconds. After that, it begins to sound as if it's struggling, and then it dies. So the inspection starts. Well, it turns out the MAF isn't providing the voltages that the book indicates it should. That's easy enough, and we replace the MAF. The only problem is, with the replacement MAF, it won't run AT ALL.
Well, other experimentation starts. We unplug the connector for the MAF sensor. Now the car starts and runs (although when taken for a test drive it sputters whenever the accelerator is pushed). Another thing that we did was disconnect the air line coming out of the MAF from the engine while leaving the sensor itself plugged it. The engine would run this way as well, although poorly.
We seem to have run out of ideas after trying/checking the following things:
Replaced MAF Shorted MAF ground pin directly to ground Disconnected MAF (see above) Disconnect air line (see above)
And also of note is that the oxygen sensor has been replaced.