greencactus3

Hi guys, just bought a 90 3.0 4wd
problem im having (among many) is a bad idle (just like when a major vacuum hose is unplugged) when

1. engine is at operating temps, (high idle is smooth when cold)
2. brake pedal is pressed. (idles fine when not on brakes)
3. t-case is in 2wd. (4hi, 4low idles fine)

I'm pretty sure i have a vacuum leak somewhere, but cant seem to find it (already washed off a good 30 lbs of mud off, probably 100lbs of mud still caked everywhere)
anyone have a good guess on where it might be leaking?

xxxtreme22r

if only on brakes, try removing the vacuum line from the brake booster and plugging the line and see if it goes away, if it does, then your brake booster is bad.

Also what is your idle at before hitting the brakes?

greencactus3

I will try that later tonight, and if you are asking for an RPM, I have no clue, no tach, but it sounds about right. 900rpmish according to my ears

xxxtreme22r

not sure if the 3.0's are the same, but I think they are, if your idle is too high and you hit the brakes you will have idle issues as well. But rule out the booster first. Just be careful, cus you will loose your power brakes. Not sure if this only doing it to you when driving or just sitting still as well.

greencactus3

I plan on getting a tach soon for easier troubleshooting soon, but the idle does not seem excessively high to me.

this happens both while driving and stopped.

thanks for the quick responses

xxxtreme22r

hmmm I just noticed you had also said not when in 4wd. ADD or manual hubs? If ADD check the vacuum lines for the ADD system as well. Not much more I can help ya with with the ADD system though.

greencactus3

is ADD the auto locking hubs?
I have manual locking hubs on mine.

xxxtreme22r

yes ADD is the auto locking hubs. Was the truck originally ADD or no? If original manual hubs, not sure why you are not seeing a change in idle when in 4wd. As to me if no ADD system exists it should do it in 4wd as well.

greencactus3

i have no idea. jut got the truck 3 days ago. has had manual hubs since i got it haha.
any way to tell?

xxxtreme22r

If the P.o. just slapped some manual hubs on without changing out the front axle tube, you should be able to see the ADD actuator on the one side axle tube. I can't remember off hand which side. Otherwise it will just be a straight tube on both sides.

I don't know the physical differences in the transfer case though. So if he did happen to change the front tube, I personally don't know enough about the ADD system to tell the difference.

greencactus3

front axle tube? I have IFS though?
didnt have time to get to any of that tonight, got exterior lights and brakes working, so big progress!

TJ96TLC

Just had this same issue, corrected timing and lowered idle and its gone.

xxxtreme22r

Toyota ADD front axle actuator will be on the passenger side.




Toyota non-ADD axle will have tubes on both side that look like the drivers side of the ADD axle.

greencactus3

I see, thanks.

I will try to drop idle and see if that helps, then timing.

how should i set idle without a tach? just go low until either it helps or until it is rough and then up a bit?

blake.nemitz

i had same problem but was caused by the wrong vacuum hose going to the egr actuator, the egr would open when i stepped on the brakes and it would run real rough almost die until i cam to a stop then it was good again wierd??

greencactus3

tried this. makes no difference.

Still chiseling out the caked mud to see the axle tubes.
got a glimpse of an oil filter last night.
maybe ill be able to do an oil change tonight if i keep chiseling

greencactus3

dont have ADD, have the idle stop all the way down so i cant bring idle lower (still sounds the same, didnt get many turns on it before it was all the way in.)

ordered a tach,

so only idea left to try out is check timing?

Cyberman

Make sure the vacuum hoses are going to the right places as posted above. I doubt it has anything to do with ADD, if you had it, cause you said that 4WD works fine. There are a bunch of vacuum lines that control the idle (power steering, AC, etc.) so checking those out on the passenger side of the truck might help.

greencactus3

there are sooo many to check!

any ideas on which ones would affect idle this way?

Cyberman

Yes there are many, and they could all affect it (especially if they aren't on the right ports). I's probably start with the steering idle up and A/C.