Q: Car starts but will not run

You should not replace any parts, at all, unless the part is diagnosed as not functioning. ECU’s rarely fail (fully 50% of warranty returns on ECU’s have absolutely nothing wrong with them).

If there is a spark at the plug (the plugs themselves have to be evaluating for possible fouling) and there is fuel supplied to working fuel injectors (there could be fuel pressure but injectors might not be functioning due to electrical fault) and the engine doesn’t start, that means there is a mechanical problem.

But, I would first check to see if the injectors actually function. One way to quickly determine if it is a fuel versus ignition issue is to introduce starting fluid into the intake. If the engine runs momentarily using starting fluid, that means that you have a fuel supply issue.

YourMechanic deals with hundreds of no start diagnoses daily and could diagnosis the trouble you are having in a quick mobile visit to your home.