I had a 90 300zx TT that blew out 5th gear while cruising at 70 once. I also lost a timing belt on that car. I lost a head gasket in a 90 CRX Si I had with 176k miles. I was running with no fans, no intake filter, a clogged cat, and hadnt changed the oil in 10k miles when it happened. I had a motor ready to drop in, so I decided to see how much abuse a d16 could take (in sum... A LOT) I once grabbed a handful of road debris, (you know that fine grit, leaves, and crap) and tossed it into the throttle body while yanking the throttle cable. It choked for a second, but kept running for a couple thousand until the head gasket went in a furious way.
About the Fan speed... I found the problem to be the connector to the actual blower resistor. The 4 pin connector had melted and distorted a little. I pushed the pin around with a screw driver and it now works again. If it happens again I'll just cut off the connector and leads at a junkyard somewhere. The resistor pack itself was fine, although a little rusted. It seems that the connector is yet another weak spot in the fine XJ electrical system.
