Re: 4x4 problems- 99 Ranger
I had done some of those same "play with it till it works" type diagnostics. I did a bunch of research online & found a lot of threads w/similar problems- I guess Rangers are notorious for this. A lot of the gear-heads on these say "scrap the automatic 4x4 hubs & go for the manual hubs" which may be an option later, but I just got married, had a garage replace my fuel pump ($800+) & had Christmas & I'm not looking to dump another $500+ on my truck right now. I found several threads describing these temperature problems w/the 4x4 engaging that said it was the Control Module, which is a cheaper fix ($80-$100). I also found a few that walked me through servicing my hubs myself, incase they were just gunked up & needed cleaning. They reccommend you do that every year or so...I was a few years behind schedule.
I took apart the hubs, cleaned & lubed everything & reinstalled them. I also checked all the fuses & relays & cleaned the electric terminals on the shift motor. The past 2 days I've had no problems with my 4x4 at all. Engages & works just as good as it did this fall when temps were well above freezing.
If it does crap out on me again, I'll try changing the module, but till then, I'm staying as is. Thanks guys & good luck. I can steer you to some of those threads if you need, just let me know.