Cadillac Repair: 4.9 run after, lock cylinder, battery cable

Question
why didn't my 91 4.9 shut down when I pulled the neg cable?  My ignition key messed up and I had to go to the battery but when I removed the cables the 4.9 kept running.  I had to remove vac lines to shut it down.

Answer
NEVER EVER remove a battery cable to shut off the engine as you can SEVERLY damage the vehicles charging system as well as the electronics.

The reason it did not shut OFF is because the alternator was running providing the electricity to run the engine.

You need to replace the ignition lock cylinder in the steering column and purchase a new blnk key that has a resistance reading EXACTLY the same as your original key and have the same grooves cut into the new key that is cut into your old key.