87 Gl Wagon, non-turbo. Regular ea-82 with hitachi carb, recently swapped the carb, it finally works correctly for the most part. After the swap, I set the idle dead on 900 rpm, only it walked up and down about 200 rpm while idling, but was around 900 in general. The next day after it was all warmed up and what not, the idle idled steady and 1400 rpm or so, not much wandering around. So I set it back down to 900, and this time it was rock solid at 900. Well, the next day, I let it warm up and disengaged the choke, only now it didn't idle at all. Pfff. I turned the idle back up and set it at 900, and the story starts all over from here. I continue to turn it between these points every few days. I don't figure it's the air temp. or anything, since it's pretty much been consistent through the problems. I didn't do anything else other than adjust the idle. Ignition problem?

I would think maybe an intermittent vacumm leak, possibly from the throttle shaft. The throttle shaft bushings on Hitachi carbs do wear out and allow extra air to enter thus throwing off the mixture/idle. Only way to repair is a complete rebuild including rebushing the shaft. Have had the same experience with Hitachi carb on old Datsuns.