I just recently bought an 89 4x4 pickup for a hunting/bush truck. It has the 3.0L V6 with 5 speed manual tranny. Problem I have is that when I put it in 4wd, engine won't rev past 1500rpm when it's warm. When it's cold, it won't got past 2500rpm. It's sounds just like the rev limiter is not set right. When I put it in 2wd, engine run's perfectly fine. Right away I asumed that one of the vacuum lines going to the front diff was leaking some where. I found nothing. Line's are in good shape and the solenoids for them vacuum lines work fine. I check all the wiring for anything that didn't look right. I'm stumped. Wondering if anyone has ran into this problem before or know yota's better than I.

Don