So, I just finished my 3.4 swap, and everything seems great. The car idles fine, turns right over, and sounds amazing. However, whenever I let go of the key, the car shuts off.

When I first suspected that it was the key position, instead of a major problem, like compression, or over-tight rockers, I capped the yellow lead of the clutch switch off, and wired the purple lead (which goes to the starter solenoid, and the CRK fuse) into a switch, which I ran to the battery. This way, I could hold the key in start, but stop the starter once it turned over. This worked, and I got the car to idle and run very successfully; but I cannot release the key.

With a voltmeter, I have verified that in RUN, the injectors, the ignition coil, MAF relay, and certain pins on the computer all receive 12 volts. When I turn the key from OFF to RUN, the fuel pump primes.

At this point, I'm really not sure where to go. I'm looking for any scraps of wisdom that you all might have.

 

For anyone else with the same problem, I finally resolved it.

The problem was a combination of two things:

1. The configuration of the ignition switch: perhaps the park-neutral stopper knocking the switch out of RUN? I swapped steering column with switches, and the problem was resolved. I later swapped the old switch back in, and it still worked, so the switch was electrically sound.
2. The tachometer. Yes, the tach. After I fixed the switch, the car would run rough or stall, with the tach dropping to zero frequently. I thought this was the distributor, or the coil, but both were new, and after hours scouring over the shop manual, I realized that a short in the tach would prevent the secondary coil from ever picking up the change in current needed for induction. Swapping in the gauge cluster from my 85 fixed it.

 

Good find. It's nice to know these things. Thanks for sharing!