02 Sportage 4wd

[chadmpiatt]

02 Kia Sportage 4wd jumps into 4wd while driving and make a popping and grinding noise, i don't know why. Can anyone help me?

[LMP]

Common...this means that the vacuum solenoid valve is leaking vacuum into the hubs. Just for testing, disconnect the vacuum tube to the hubs at the solenoid and see what happens.
www.avigex.ca/kia/vacsol.jpg

INdeed, applying vacuum hubs while the t-case is still in 2WD means the hubs will force the front half-shafts, differential and front driving shaft to catch up with wheel speed.....which might already have damaged the hubs...so stop this at once.
YOU can run the vacuum solenoid electrically on and off and run wd-40 through the ports with engine running or using compressed air to try yo dislodge dirt in hope it will become tight again. I did it once but eventually, had to change the original hubs to WARN auto-mechanical.