Hey all this is my first post. I am on the VH Facebook pages, but i figured i join here too. Still having issues with my VH45(its in a s14)…Anyways, here is whats going on. On a COLD start the engine idles perfectly smooth for about fish seconds, then the misfire begins. It is a pop pop pop pop noise, sometimes it is a consistent pop, sometimes its more of an inconsistent pop.. once in awhile (maybe 1-2 times a day) while crusing in 2nd or 3rd around 3-4k rpms, the motor kinda of stumbles, doesn't really lose power just sounds like its misfiring even worse than usual. It only does it for a minute and then "cleans" itself up. Only other issue i am having is once fully warmed up, my idle will hunt up and down, only once or twice has it ever shut off when i put the clutch in. I have replaced/cleaned the maf, the shop who did the swap said all the coils are good, the knock sensors have been bypassed. I have injectors laying around that i am going to replace, just haven't had the time to get to it yet. The only thing that is making me scratch my head is why it idles just fine on a cold start for 5 seconds then starts misfiring. No codes are being thrown either.

here is a video when it inconsistently misfires
https://www.youtube.com/watch?v=UBqfiUiGJHA

Maybe needs a new Coolant temp sensor or mafunctioning IACV? Ive had to replace/service both on all my cars, s chassis and Q45 combined.

Nissan has redundant coolant sensors on their older engines. They have one sensor for your temperature gauge and another for the engine computer. For my 240SX, it would randomly stall for no rhyme or reason. My in vehicle temperature gauge read close to a middle reading. One day I got a one of the consult cables where I could read all the engine data. Turns out that the values on the coolant sensor were jumping around and it was running rich when fully warmed up. I would check that out. FYI, the one with the two connectors is the engine ECU sensor, the single connector one is for your gauge.