1993 Infiniti J30 Rough Running Diagnostic

Customer brought in this low mileage (101000) 1993 Infiniti J30 with a rough running issue that several shops could diagnose. Let me show you how I approached the situation. Spoilers below this line........ Based on my test drive I was reasonably certain my issue wasn't a fuel supply issue from the pump or filter, wasn't plugged exhaust, wasn't engine mechanical, wasn't MAF sensor. Most of those things will effect all cylinders and I was feeling a roughness on just one or two cylinders. The roughness increased as the car warmed up. My first step after a drive around the block was to scan the vehicle. I was fortunate enough to have the old Nissan adaptor I needed and I was able to retrieve a code 51 - injector circuit open. This is where I would have been heading next because its a common issue on the Nissan's from the 90's. I used the guided component test meter in the Snapon triton D10 to get some information about the best place to test the injectors which led me to the two injector bulkheads under the hood near the back of the intake. I placed a low amp clamp set to a 20 amp scale around the power supply wire for all six injectors and notice one that didn't look like the others. Now we need a sync channel to find out which injector is failing. With my second channel connected to the control side(negative side) of the injector we identifies that cylinder 6 injector is the bad injector and the resistance is higher than normal causing low amperage draw. I measure the resistance of injector number six after removed and it was 20 ohms cold and 33 ohms after a soak in 150F water. I didn't measure the other 5 but I did replace them.