Leaderboard

Good work. Annoying that it doesn't know what's up, but that's OBD1 for you! You can test it with a plug, yes. I use an old spark plug for this so I don't have to take the existing plug out. I like doing it that way because it makes it harder to zap myself. When I don't have a plug handy, I stick a screwdriver where the plug would go, hold it by the plastic handle, and hold the shank maybe a quarter inch from the manifold while cranking. Otherwise you can just hold the wire (by the insulation!) so there's maybe a quarter inch spark gap between the intake and the end of the wire. This is easier with the coil wire. Speaking of zapping yourself, I haven't heard of anyone being properly injured by it, but that doesn't mean it's a good time. The ignition system should be putting out something like 28,000V. Be careful where you put your fingers, and don't hold onto a damaged wire. You could also start with the carb cleaner if you're more comfortable with that. If it kicks on spray, then you know it has spark, and you can skip messing with the plug wires.

I just stumbled across some info on the 190F thermostat. It does exist, but Nissan warns of cats and dogs living together if it's used in a VG. The problem with the 190F thermostat is that the VG does not run at the temperature of its thermostat. The VG's thermostat is located on the lower rad hose, the cold end of the system, so the engine actually runs 10-15C hotter than its thermostat. Nissan's target for max engine temp is 90C (194F). 76.5C (170F) plus 15C is right on target at 91C. 82C (180F) plus 15C is pushing it at 97C, but apparently Nissan was comfortable with this, because NTB94-020 recommends swapping in a 180F thermostat to help the heater keep up with winters on Hoth (like Adam did), and (as Adam noted) they later spec'd 180F thermostats for the VG33E. 88C (190F) plus 15C is 103C, and apparently that's out of Nissan's comfort zone, because they warn that it could cause overheating, detonation, engine damage, computer trouble, and a voided warranty. The 190 thermostat was used in earlier (pre-VG) Nissan engines. They had the same 90C/194F max temp target, but their thermostats were on the upper rad hose, so they didn't have that 10-15C offset to factor in. TL;DR: 170 is stock, 180 is OK, and 190 is not recommended.