I bought my 93 300zx na about a month and a half ago. It ran great when I drove it home after buying it but since then I’ve been chasing a weird idle issue. The car runs fine until it warms up then it starts bouncing the idle around. It’ll sit at 700 then down to 300 before catching itself and shooting back to 700. I’ve done plugs and I went ahead and did coil packs since they tested low. I cleaned the maf and checked temp sensor connection but no difference. When I use anything that draws power it bogs the engine more. Also when holding speeds while driving it has it has a stutter. The car doesn’t backfire or anything but it stutters. I have no idea what could be the issue.

 

Your issue sounds like one I had.

700 is too low an idle on my 93NA. It likes it much better around 900. Since I got it new, it idled at 900. !t was tune up recently and the idle was set to 700 and after that, every red light or stop sign I stopped at, as I slowed and stopped, the idle would drop to 450-500 or lower for a second and then recover back to 700, or stall 50% of the time. I adjusted the idle up to 900 and fixed the stalling issue. Car now runs great.

Adjust up the idle up

There is an idle control valve or regulator on the back of the engine (near the firewall) on the upper driver's side, with a screw point towards the driver's side fender. Just unscrew (counter clockwise) the screw to increase the idle. Count the number of turns. See what happens. You can always turn the screw back if needed.