Guys,
FYI, I have a 1993 4x4 ext cab SR5, 3vze with 250,000 miles that I purchased brand new. I have always taken good care of it, but have recently had problems with it. Just passing along info: problems included rough idle, trouble code 25, cruise control not working, and 4x4 not engaging. I found that the EGR valve was leaking, the air intake hose between the VAFM and the throttle body was split at the TPS causing a leak. I also found a vacuum hose disconnected for the cruise control near the firewall (driver side) that solved the cruise control problem, but I still had the problem with rough idle and 4x4 not engaging. I tore apart the dash, and it wasnt the light bulb for the 4x4, it turns out the two solenoids (VSV) mounted on the engine compartment side wall were good, but the vacuum line between them and the actuator for the 4x4 had a slice in the vaccum hose causing the 4x4 not to engage. I replaced both vaccum lines and it worked! A nice side benefit was my rough idle returned to normal. Hope this helps someone out there.

 

Vacuum leaks=rough idle. Between the 4x4, cruise, and EGR I would expect a pretty rough idle. Did you ever do anything with the EGR? If it is stuck/sticking/leaking, you still may have a vacuum leak.

 

Replaced it, even after replacement it still leaked at the screw on connection, had to use high temp silicone