have a 91 z32 na one cylinder misfire at low rpm below 2500 after that seems fine spark plug good, coil pack good, compression good, injector new, power transistor unit good, connectors to injector and coil pack have voltage and signal, what else could it be thanks

 

Did you make sure the fuel rails aren't leaking? Is the injector new, or used? Does it ohm correctly? Have you checked the plugs?

 

no leaks on fuel rail, spark plugs new, new remanufactured injectors, all injectors and coil packs ohm good , upon further testing does this all the time stopped at idle, and when driving it hardly misses.

 

You've done power balance test and confirmed by ear all of the injectors and coil packs are working?

 

did the power balance test, switched the coil packs around still on same cylinder, also checked the injector and don't hear any malfunction. only other thing i can think of is ecu or harness. is there any way to read coil pack signal on connector.

 

Stick a long screw driver to the coil pack and injector then put your ear on it with the car running, if you hear loud obvious clicking then it's working. Also what did you get on the compression test compared to the rest of the cylinders?

 

ya did the screwdriver stethoscope and ticks without skipping a beat and got 165's, 170's across all cylinders on compression test