A couple of weeks back my JDM E9 GSR just dropped 2 out of 4 cylinders for a few seconds while cruising on the highway and then came back on again. I thought it was a one off incident until it became more and more frequent uland one day I pulled over to check what the hell was happening.

Ignition coils were fine, I pulled the connectors one by one to test them. When I pulled the injector connectors to the middle two, there was no change. The engine didn't die out or anything. All this while it's a very rough engine running on 2 cylinders. I confirmed this by putting a screwdriver to the injectors and I did not hear the middle 2 clicking away.

I didn't have a spare set of injectors so I swapped them around to test and weird enough, the middle two still was not firing!

Brought the car to my mechanic and he checked the wiring from the ECU to the injectors. There's power running through the wires but no injector pulse.

What in the world could be the problem? Cam sensor? Crank sensor? I would have thought that if either sensors had problems, the engine would either not start or all 4 cylinders would still fire but run very roughly.

 

You can use an 12V LED and stick it in the injector connector and see if it is flashing, which would indicated it is seeing the proper signal. Since it is a diode you likely need the polarity correct in order for it to work so just flip it around if you don't see it flashing initially. For the injector, you can use a 9v battery to test them to see if they are opening and closing. I would start there just to validate what you are seeing.

 

Check this post and look at post # 20. Has helpful info on the injector resistor pack. (location, part number, troubleshooting tips)

https://www.evolutionm.net/forums/ev...unction-2.html