I just got my engine rebuilt and it's idling at .4k or so, and it feels like it's about to stall. I need to know what I need to do to raise it and also where exactly it is. On my 2nd gen, all I needed was a flathead screwdriver and it took me about 30 seconds.

 

man, nobody knows?

 

3rd gen 4Runner utilize an IAC (Idle Air Control) valve that is controlled by the ECU and allows a small amount of air to bybass the throttle body into the plenum . The more the valve opens, the higher the idle will be and you cannot directly adjust it unless you mess with the computer.

If the IAC is the culprit though, one thing you can do is clean it, and there are numerous write-ups on how to do that, just search. BUT, considering that your truck is a '99 I am going to put my money on a bad vacuum hose, because it takes a lot to gunk up the IAC that fast (unless you have been driving around with no air filter or a very dirty one).

EDIT:
I must've missed that you just rebuilt it. Maybe I ask why? These engines are supposed to last much longer. Still, I am gonna put my money on a disconnected/bad vacuum hose, but then again it could be many other forgotten things during the rebuild.

 

I fried some pistons, busted up a connecting rod and the head gasket. It was my fault. I was doing some major tune up and while flushing out the radiator, water/coolant must've leaked or clogged by the damn solution or something.
Anyways, my air filter is brand new so I should check the vaccum hose?

 

Well if it's a new IAC (not dirty) then the only thing I can think of would be some vacuum hose being disconnected. I know when I disconnect my PCV line, the engine sounds like it wants to die and idles really low. I am not a mechanic by any means, so there might be something else causing low idle, but I am just gonna stab at it and say that the ECU would be able to adjust for any low idle condition, because I just don't see something maxing out the IAC, but I might be wrong.

I really hope more people chime into this and you find the solution to your problem. Good Luck.

 

Vacuum hoses usually cause a high idle condition so I doubt that is it but you'd do well to check them all anyway and make sure they are all hooked up to the correct places. The IAC may be causing this issue so it would be good to clean that and also just clean the throttle body, carbon buildup can cause low idle as well.

 

at a glance.. seems like all the hoses are connected correctly..
MTL, I would think a hole in the vaccum hose would cause a low idle, since there's low or no air flowing through.. I'm running out of ideas..

 

Here's the verdict.
I've took out the throttle body completely. I used a throttle body cleaning solution from walmart for $1.70 and I also used engine cleaner to clean everything and get all the grease out. Now my runner runs perfectly. It was idling at .6k, about to die and it's at around .75.

 

well, so much for that... it ran perfectly for about a week and now it's back to low idle... did my throttle body get dirty ?