No idea what is going on. In 2wd my truck runs great. I have a 95 4runner with 3.0. As soon as I put it in 4wd and start to accelerate it starts jumping all over the place like someone is cutting the fuel. Surging bucking all over. As soon as I let off the gas it coasts totally fine. There are a bit of issues that I would have thought this was accept that in 2wd the vehicle runs super smooth. Could this be EGR valve related?? Two days ago my 4wd was fine. Any help or brainstorming would be great. Have tried other forums with no responses. Thanks !!!

 

Your in the dirt or snow??

Torque bind if it is cold it is easier to feel it seems

Do you have ADD ??

Might be a vacuum leak when your in 4x4

 

This is in the snow or dirt or any conditions. I do have ADD. Checked the vacuum lines to the actuator seem ok. It stays in 4wd just bucks like crazy throughout the entire rpm range. Worked fine a few days ago. Thanks for the input.

 

If the truck is running fine in two wheel drive and no issues, I suspect it is binding when 4 wheel is engaged. All four tires the same size? Having the correct tire size makes a big difference. Even having the correct tire size but two different brands can make a bucking/growling issue. Different brands are not always the same size. For example you may wear a 9 1/2 Nike shoe but a 10 in a Converse shoe. Check your tire size and brand and all match.

 

 

Ok. I might have found something. I noticed that my vsv for my ADD has only one hose running into the wheel well to the vacuum canister. The nipple on the bottom going into the wheel well has no hose. Not sure where this hooks up to the vsv or the canister but I will look farther. I’m curious as to if this could cause my condition as I feel the add is functioning now and 4wd light stays on through the hole lurching around.

 

Ok. I might have found something. I noticed that my vsv for my ADD has only one hose running into the wheel well to the vacuum canister. The nipple on the bottom going into the wheel well has no hose. Not sure where this hooks up to the vsv or the canister but I will look farther. I’m curious as to if this could cause my condition as I feel the add is functioning now and 4wd light stays on through the hole lurching around.

 

It has to be some place in the ADD system other wise it would happen all the time.

Do you have a volt meter if the ADD system is pulling the voltage down it can make the engine miss and sputter

Not as likely as a Short should cause the circuit protection to open

 

 

If you have a missing vacuum hose that could be upsetting the engine when the VSV switches to that open port. Try capping that port and see what happens. Your ADD could be stuck permanently in gear (the green light would still switch on/off with the transfer case position). You can check the ADD by putting the vehicle in 2wd with the engine running, and then shutting it off and crawling under it and trying to rotate the front drive shaft. It should rotate fairly easily. If you can't turn it your ADD is stuck in gear. The stuck ADD won't explain your engine issue, but would explain why 4wd works even with the disconnected vacuum hose.

 

 

Ok. I replaced egr modulator with correct one and replaced every vacuum hose. I am still having issues with 4wd. I would think that if something g was slipping my rpms would jump as I lurched around. All rpms are affected. Found a straight dirt road and pushed it to 35 mph and experienced the surging all the way though. Every time it surges the rpm is dropping. Literally like I am taking my foot off the gas. It feels like it’s “missing” however there are no problems in 2wd. In fact it seems a little better after all the new vacuum hoses. The only thing I did not get to replace is the orange vacuum check valve coming off the pair hose. I am really stumped. Could my throttle cable be out of wack. It only in 4wd???

 

when you say jumping around, you mean the engine is stalling or the drive train is binding up? not sure what all has been done to the truck but i bought a half done project 1st gen a while back and it had a factory 4.30 rear with a 4.10 front.. no drive shaft when i bought it so i didnt notice until i got one put on. any play in the front drive shaft? check for grease-locking on it, but i think with add its always spinning anyways.

 

maybe if you took a video, "jumping around" could mean a lot of different things. Are you putting it in 4wd hi or low? Sounds like it's an automatic?

 

 

 

At any time have you measured system voltage while this is happening??

It is either electrical or as you think vacuum just because you replaced the hoses does not mean something else has not failed causing it to be pulling extra air

 

ok. I don’t know where to test the power. However I ended up getting the check valve going to the pair and then doubl checked all vacuum lines. I decided to cap the ADD Lines and the line going into manifold and at diff. I did this to see if doing the add delete would solve my issue. As soon as I shift transfer case to 4wd I still here the click and the rpms drop. 4wd is not engaged because there is no vacuum. Start driving and same thing happens. As soon as I push hard on gas it starts cutting in and out after getting to about 40 mph in 4th and my throttle evens out it smooths out. As soon as I push the pedal hard for power it is sluggish. So what is happening at the ecu when the transfer case lever is shifted to 4hi and the rpm drops? This is totally messing me up. Please any info is helpful.

 

Once again 2wd is flawless and runs smooth with plenty of power.

 

Next thing you might try is to pull the connector off the transfer case, so that nothing electrical knows whether you're in 4wd or not. (the connector is up on the passenger side of the tcase, toward the top. Not easy to reach, but doable.) If the problem goes away even with the tcase mechanically in 4wd, you know the problem is electrical. Then you can start breaking the connections further and further from the tcase until you find the offending part.