First of all i would like to thank those who helped me with the check engine light prob,you were right on the money.Changed the idle air control valve and problem solved,expensive bugger.Now a new prob if you can help.4 wheel drive not engaging,light flashes,relay clicking under dash,checked for leaks in vacuum system could not find any.Checked actuator under battery,seals not busted or leaking.I pulled off the vacuum hose at this actuator and the cable pushed out like 2 clicks,hooked the hose back up and it pulled it right back in.There is no problem with the heater controls so i figure there is no problem with the vacuum system.The problem started gradually this winter,it would engage but take 15 to 20 minutes of the truck running before it would work but now nothing.help appreciated .

 

could be somethin with the transfer case or the vaccum switch is bad on the transfer case. usually with the 4wd goin out theres only a few reasons for it either its the vaccum actuator, vaccum lines, or transfercase. if its not anyone of those then it would have to be in the front diff.

 

Try this simple fix located in the other thread.

https://blazerforum.com/m_157073/tm.htm