91 240sx w/ DE Throwing codes 12 21 and 34 need help

[Lockleaf]

1991 240sx coupe w/ KA24DE

Code 12: Air flow meter

Code 21: Ignition signal

Code 34: Knock/Detonation sensor

The short version: Could a DET sensor not being connected cause all three of these codes to come up and the car to smoke and run poorly?

Could an ingnition switch that sometimes fails to disengage even with the key out cause the ignition signal code?

The Long version: Ok, I bought this car for cheap a few days ago, not running. I pulled the codes and found a bunch and fixed them. I finally got the car to start just now, but it runs really choppy and smokes a ton (catalytic has been removed) Loads of misfires.

In my investigation into these problems, I noticed that the length of wire from the DET sensor to the wiring harness (what connects the main harness to the sensor) (that part that goes under the intake manifold) is not there. In other words, my det sensor is not connected at all. could my det sensor cause the poor firing issue and also cause these other codes to show up?

The MAF wiring connector has been replaced in this car. It was wired so poorly that I don't think the car even knew it was connected. I just rewired with basic butt connectors for now. the MAF is clean. now that the car is running I guess I can do a voltage check on it.

The ignition switch in the car sometimes doesn't fully disconnect. My dash lights will stay on even with the key out some of the time. Could this be part of what causes my ignition signal code to come up?