KDI_CUSTOMS

Before this thread gets deleted, please note that I DID search the forums and could find any info on this issue other than stuff in 95 and up.

I have a 91 V6 pickup with automoatic trans and ADD. The engine was swapped about 3 years ago. I know 4wd worked before the swap and had not used 4wd after the swap. First time using it, I found that I had no 4wd. Swapped 2 vacuum lines and now have the 4wd light functioning. I also had a stuck solenoid (blue one) that I replaced.

The issue Im having is that the 4wd light flashes rally fast and the solenoids are clicking under the hood and under the dash. I shifted it in 4Hi rolling uphill and gave it some gas and it went from flashing/clicking to a solid light. As soon as I let off the gas, it went back to flashing/clicking. I felt the 4wd engage so I know it is working. SMH and trying to figure this out. If I find any other syptoms, I will add to the post.

Anyone have any suggestions?

Thanks
Tim

KDI_CUSTOMS

^TTT^

Rainy day today so I wont be working on the truck. Still searching the net for answers of what could be wrong.

ALLDATAdiy INFO

Have you tested or replaced the Solenoid Relay? Is that what you hear clicking?

KDI_CUSTOMS

I hear the relay under the dash clicking and also hear the solenoids under the hood. Its a constant fast click and flashing 4wd when the truck is running. If I shut the truck off with 4wd engaged, the light and clicking slows down until it just stops all together. Its almost like something is wired wrong.

KDI_CUSTOMS

If anyone has any info, please help. Dont have $$ for the stealership to diagnose this. Im almost thinking that some wires were crossed during the engine and trans swap.

KDI_CUSTOMS

Bump
Im still trying to figure this out!

UKrunner

Check your vacuum lines and accumulator for leaks.

KDI_CUSTOMS

I have a question about the VSV for the 4wd system. I have 2 valves, brown and blue, that run the 4wd. If I unplug the electrical connection to the blue one (leaving brown one connected), my 4wd light stays on when engaged. If I unhook the brown one (leaving blue hooked up) I do not get 4wd light. I tried to trace the Pink wire on the blue VSV but cant find it in the chilton. Is this the wire that runs into the dash for the 4wd light? Is it also the wire that runs to the plug on the front diff? Also, if I unplug the one VSV will the 4wd still function? Not sure whats involved with 4wd and Im still learning.

Inferno451

Something similar happened on my 92' pickup. There are two vsvs on the far left side of the engine bay (those are the ones you found for the 4wd). The connectors are the same color, size, and shape as two other vsv's (for the emissions equipment) that are about a foot to the right of the 4wd ones, you can see these in the picture below. The previous owner of my truck had accidentally switched the connectors and hooked up the 4wd to the emissions sytem, and vice versa. This was making the vacuum solenoid for the ADD system in the front differential to lock in and out depending on the signals that were supposed to be going to the EGR and other emissions stuff. There should be a wiring harness with 3 connectors coming out, those are for the emissions. The wiring harness with 2 connectors is for the 4wd. I'll bet those got switched around during the engine swap. They ARE color coded to the vsv's. Good luck!

KDI_CUSTOMS

Inferno, I checked those and it looks like they are hooked up correctly. It is light snow out so I put the truck on a hill in the yard. Put it in 2wd and rear tires spun/slipped. I dropped it in 4hi and it walked up the hill. As soon as I gave the truck some gas the 4wd dash light stopped flashhing and stayed solid. Not sure what is going on and I dont know if 4wd is actually functioning or if the rear diff is just gearing down to allow the truck to walk up the small hill.

Inferno451

Sounds like a vacuum problem to me. Sometimes you have to play with the gas pedal a bit to get the ADD system in the front differential to lock in. There's a switch in the transfer case as well as one in the front differentia; BOT?H to be tripped for the 4wd light to go on. The one in the transfer case is tripped as soon as you move the lever down into 4hi, but the one in the differential isn't until the sleeve for the ADD actually moves. If I'm stopped I usually have to roll a few feet and then play with the gas to get it to go on, and if i'm rolling i have to let off the gas a little bit. I'd probably trace the vacuum lines down to the differential and make sure there are no holes, etc. That sounds like your best bet. For a test, disconnect the 2 vacuum lines to the front differential. With the engine running in 2wd you should be able to feel a vacuum from (only) one of them. If you put it in 4hi or 4lo there should only be vacuum from the other one. My problem was that there was vacuum from both sides, which made the differential try to lock and unlock at the same time. That COULD cause a flashing 4wd light. Please let us know what you find!

sebastianholmes

time for a manual hub swap!

KDI_CUSTOMS

OK here is where Im at. I checked the vacuum lines at the VSV's and everything seems fine. I traced them down to the canister in the wheel well to make sure everything is good there and back up to the oneway al the way up to the plug on the intake. I then unplugged bith the electrical plugs. The brown plug has constant power when unplugged but the blue has none. Cycled through 2wd and 4wd and still nothing on the blue. Plugged the brown in and left blue off and now I get power at the blue in 4wd. When both are plugged in I get the flashing dash light.
Now my thought is that the blue is supposed to get power when shifted to 4wd and turn on the vacuum and the brown is supposed to turn off. Shift it to 2wd and blue shuts off/brown comes on. So why is the brown constant power? Bet this is why I have a flashing light!! I got some more testing to do later.

KDI_CUSTOMS

Is it a possibility that my ADD (Fuel) Relay on the steering column is bad? Not sure how to check it other than go to the junkyard or stealership and replace it. I also went diggin around for the 4wd computer but cant find it. I have 2 plugs behind the ashtray area but no computer there. Where is it on the V6 model??

So tired of no 4wd....I wanna go out and play in the snow!!

justin_4runner

pm sent... check mail...

TNRabbit

I had a similar issue that ended up being that the center support bolts were backed out @ halfway. It was causing some type of short. Tightened them up & problem solved! That was 37,000 miles ago.

TNRabbit

...by center support, I mean under the tranny...

KDI_CUSTOMS

Gave Justin-4runner a call and he explained a few things to me. I did a little pokin' around on the front diff and figured out that the front differential is locked at all times. Both front wheels spin together.

First off, I put the truck up on jackstands.

I unscrewed the electric plug from the front differential to check and see if the sleeve inside is moving. I started the truck up and kept it in 2wd. Pushed the plug plunger down with my thumb and the sleeve didnt move. It stayed closed toward the pass side of the truck. I then dropped it into 4wd and the 4wd actually seemed to lock in. I have all 4 wheels spinning. I pressed the plunger down and the sleeve slides off to the drivers side and disconnects the front wheels. I let it go and it slides back over to the pass side and bangs into 4wd again.
This seems backwards to me! Id think that if the plunger is pressed in it engages the VSV. Id have the 4wd engaged and I should have vacuum on the front of the differential, not on the side. Vacuum on the side should pull the sleeve to the driver side and disengage the 4wd by having the plunger drop in and disconnect one of the VSV's.
If I swap my airlines back to the way they were originally I get no 4wd light or 4wd at all, but the sleeve disconnects and each front wheel spins on its own.
Im at a loss here. Im sure I will figure it out soon. Just thought Id post up so others with the same issues can learn.

justin_4runner

ok confused a little, when u had it in 2wd the two front tires spin and when in 4wd they dont? if that is the case then yes your vacuum lines are backwards, i have inserted a photo with what sides the lines should be on. 2wd and 4wd sides. the switch that u where pushing in on should be pushed down when put in 4wd. i had found a repair manual for the add system but i cant find it now, but if u hook me up with a fax number i can fax it to you tomorrow, u can call me if need be too..

KDI_CUSTOMS

OK, this is what happens for me. I unscrewed the plug (yellow dot). I put the truck in 4wd while running. If I press the plunger in on the plug and the sleeve slides toward the driver side (2wd side) and the 4wd light comes on. If I let the plunger go, the 4wd light goes out and the front locks back in (4wd side).

Now, if I reverse the vacuum lines on the differential and try it I get nothing. No light, no sleeve movement, NADA!!

Wife seems to think its a faulty plunger switch. Im gonna go over the entire thing again after lunch since she is off today and can help me out.