Calling all VQ30DET experts!
I have a 2002 Y34 Gloria with the VQ30DET engine.
I've been having issues for the past month now, at first it was a minor misfire that would clear itself up after a couple minutes, but then worsened over time. Eventually cylinder 6 would not fire at all. I found the culprit to be the notorious number 6 spark plug chamber oil leak inherent in many VQs, killing the coil pack. I replaced the plugs and the bad coil pack. Plus I sealed up the chamber with some RTV; I saw a guy do this for his 350z and he confirmed he'd gotten 70,000 miles out of it with no issues and I haven't seen that re leak so far. I had to remove all the air intake piping and the top of the intake plenum with the throttle body attached to access the valve cover above cylinders 2, 4 and 6. Since I've done that, the engine still misfires. But the thing is, it runs fine cold with good throttle response right through the rev range and driving whilst not quite fully warmed up gives nice, peppy responsive action. Once it gets to full operating temperature, it starts to go downhill. The misfire will start up again minor at first, then worsen until it seems that one cylinder has completely given up on firing. I let it cool down, start it up again and it runs fine. I took it to my local nissan dealer after I'd changed the pack and plugs with no change and they pulled the code P1320 Ignition signal primary. They then pointed out the bad connectors on 4 and 6 which I've just replaced with good ones. I'm finally at the end of my knowledge base and would like to put this out there to see if anyone has any ideas. I've checked for head gasket failure symptoms and my coolant and oil is looking as it should.
Any ideas to help towards finding the cause of this issue are greatly appreciated.