alt Hacker Newsmost likely, his new non-redundant non-operating-temperature-rated ECU is just turning on the fuel injectors, and completely ignoring all feedback the original ecu used. so until he hears the knocks, he will think he "fixed" it.
yolo engineering for ya.
If you just turn the fuel injectors on all the time, they will overheat and fail very quickly and the engine won't run.
I've got a "get you home box" for EFI systems with separate ignition, like Bosch LE-Jetronic that I built a few of as clones of an insanely expensive device some 20 years ago. It really just consisted of a couple of 555 timers and a bloody great MOSFET, with one 555 wired as a Schmitt trigger picking up ignition pulses and the other delivering a 1ms pulse to the injector coils every time the spark fired. This dribbled enough fuel into the engine roughly proportionately to engine RPM to let you drive it slowly to somewhere you could work on it safely, or even just onto a trailer.
And of course, Speeduino, Megasquirt, and a bunch of others are a thing.