Hey scotty, just got my car back from getting a junkyard engine put into it after the old one was deprived of oil. Im having a cylinder 3 and 4 misfire and my mechanic is saying thats the fuel injectors arent getting any signal and that it could be the computer. I changed the computer and all was good until a couple of ours later when its started misfiring. Could that be a sign of a bad motor or just a short circuit in the witing?
Figuring out if this is an issue with the PCM's injector drivers (transistors) is really easy but to do it right will probably cost you $20.
Your fuel injectors are "ground triggered" by the PCM.
So you'd want a "reputable" pinout chart of your PCM connectors to identify which pins are those 2 injector drivers. (that's where paying $20 for a 1 month subscription to alldata diy https://www.alldata.com/diy-us/en/diy-repair-information may be neccessary)
But once you have those pin identifications, you can use an inexpensive test light to see if the PCM is switching the ground to control those injectors.
So, connect the alligator clip of the test light to the Positive Battery post.
"Backpin" the wiring connector at each of those injector driver pins for those fuel injectors.
Crank the engine.
If the light flashes the PCM is providing the Ground Switching Signal to the injectors.
I found a video of Paul Danner showing how to do this. Even though it's not the same make/model as yours, yours works the same way.
https://www.youtube.com/watch?v=kQUtAs-VrDY
