Hey guys, new to the forum here, and I just bought a manual 1996 4runner sr5 with 280k km's. So far this site has helped me out a lot in trying to get this truck working properly. One thing I'm still having issues with is the 4wd.
When I first bought the truck, it needed a battery and every time I would boost it the 4wd would work. However, ever since I put the new battery in, the 4wd is acting up, to the point where it wouldn't engage anymore. So the first thing I did is to swap the VSV hoses on the driver side fender and the 4wd seemed to work again. While driving with the 4wd on, I saw the light go off on the dash. When I try to get it back into 4hi,it wouldn't engage and the light would appear then disappear right away. Any ideas?
One thing I did notice is that if I'm driving and put it into 4hi, it will work,light comes on, but as soon as I let go of the gas the light will go away.

 

Gonna go out on a limb here. This last makes me think you have erratic vacuum due to a bum check-valve, leaky reservoir, or bad hose or connection. When you let up on the gas, manifold stops pulling vacuum. Check the check valve first. It's a $3 part at NAPA, any ol' vacuum check valve that fits the hose will do. You know, just put your lips together and blow, first one direction then the other. Should go only one way. Ideally, you would then get a vacuum guage/pump and test the integrity of the rest of the system, unless you can eyeball a bad/loose hose.

The swap hose technique is just a test--you don't want to leave it that way. You got that, right?

 

Thanks durk, I'll take a look at the check valve this weekend and post what I find. I know the swapping hoses is just a test, but my car got stuck and I had to leave them swapped. Does swapping these have any negative impacts on the truck?

 

Not short term, but you are leaving the front diff engaged as far as the TC output flange, so there is increased wear on a bunch of components and reduced mpg, assuming it stays engaged in 2WD (depends on the fault).

Did the vacuum stay on one side of the VSV's regardless of 2H or 4h or 4L?

Or did it switch back and forth?

 

Is the check valve down near the diff, or near the vsv?

And the vacuum switched when I changed the lever from 2h and 4h

 

Close to the VSV's. The VSV's have each have a hose that goes to a mini-manifold (4-way) a few inches away. One of the other two hoses goes through the fender to the vacuum reservoir. The last one goes to the intake manifold to get vacuum for the system. The check valve is a few inches down this run.

EDIT: Found a pic:



I had a 1985 BMW e23 735i that had vacuum powered AC controls. Whenever you let off the gas, the A/C would get turned into heat. The issue turned out to be the $3 check valve.

 

To piggy back on this topic, my 4x4 engages and then takes forever for it to disengage. To the point I have to stop and mess with my 4wd lever. What part or parts could this be?
Thanks

 

The front diff uses a vacuum actuator to both engage and disengage the right side CV shaft. There is one vac line feed to the electrically activated air valves on the left side fender, then two lines (one from each valve) down to the actuator. It's possible that the one that engages is fine, no leaks, but the one that disengages has some leaks (splits at either end, holes in the middle) and isn't able to pull the actuator very well. Or the solenoid air valve itself is sticking and not opening very well.

 

any one got a snap shot of what I'm looking for?
Thanks!

 

theres a good chance your 4wd indicator switch is going bad. If it doesn't work properly it won't send current to the vsv's to actuate the front diff. In the front diff itself is another sensor that will light up the dash when the diff is actuated. But they all tie together so if one switch isn't working 4wd won't light up even if the transfer case is is spinning the front drive shaft.