thedanned

Hi all, relative newbie to this site though I have been lurking/reading for a while. I, like many others it seems, have a surging idle problem when warm and brakes applied.

About the truck and problem:

1989 4Runner 3vz manual

Cold idle is about 1800, warm idle is about 1100

Throttle stop and dashpot are not touching the throttle bracket (was this way when I got it)

Idle screw all the way in to slow (like this when I got it)

Cannot find a single vacuum leak, my coolant level is ok and timing is set at 10* BTDC. All vacuum solenoids are functioning properly and at the correct time. My coolant passage through the TB is ok as well.



This all had me stumped because I had spent so much time reading other peoples posts on this problem and had tried EVERYTHING other people have tried. So I then notice that my throttle 'sticks' shut after it has been sitting for a couple hours. So I try it by hand. Sure enough, the throttle butterfly is sticking in the bore. I pull the TB off and when closed (completely, throttle stop screw is not touching remember) there is a 16th of an inch gap between the left and right sides of the butterfly, almost like the butterfly is egg shaped. I can see light between the two. It seems like I have found my culprit: I cannot restrict the air enough to get my idle down to where it should be.


My question is : has anybody else taken their throttle body off and looked at the bore? Has anybody noticed a gap? Or am I reading into this too much looking for boogymen?

I cant begin to imagine what series of events led up to the throttle stop, dashpot and idle screws being adjusted to their respective extremes. Should I adjust the throttle stop screw back to factory specs (with feeler gauges and such) and go from there or should I go to You Pull It and find another TB?

DJ99

Funny that you should mention this. A while back, when I was trying to nail down my mileage issues, I checked out, and actually replaced the TPS. When I checked it out, the throttle body bracket (?) was not actually contacting the stop. It was at least 1/8" out. This is on a VERY low mileage '93 3vze, like 46K. I ended up resetting the stop to contact the bracket when replacing the TPS, which was probably not the issue. Bottom line is: This probably is not your issue. As long as the butterfly closes, the stop is not your problem. OTOH, mine DID NOT have a 1/16" gap on the sides. That ain't right, AFAIK.

Targetnut

Yes, set everything to factory specs and see if that helps.

If the idle is still to high it could be because the auxillary air valve, (which may be part of the throttle on that model) is not closing all the way.

Jeremy11

I also have a similar problem..
When cold my engine is idle about 1300
Once it warms up its good at 800. BUT when im driving for a while and i apply
the brakes sometimes my truck will turn off completely.
Inorder for my truck not to shut off I havee to put it into Neutral and it will
idle at about 800 where its supposed to be.
I have a 1990 4Runner 3.0 V6. I dont know where to go from this.
Any help is appreciated.

PS: When slowing down the truck drops down to about 500 and drops and rises from there. Then soon dies..

limon32

I don't have any real good suggestions for you, but a couple thoughts:

My throttle boday butterfly, and ALL others I have ever seen, seal off the throttle body completely when closed. Yours seems supect to me. I would expect your throttle body thinks there is a HUGE vaccum leak with what you have described. Particularly the idle air valve is essentially useless if the butterfly doensn't close completely.

My butterly was sticking after sitting for as little as ten minutes. I took it off and sprayed it down with a whole can of cleaner. Get the aerosal type and do this, it can only help, even if it doesn't solve your problem. There are 4 vaccum passages in there that you can spray out. All three of the smaller ones on mine had chunks of carbon fly out when I did this. Once I put it back together, my initial problem was not solved but the truck idles better and has better throttle response.

(FYI - my issue was a bad EGR modulator and I think my cold idle injector isn't working).

Teuf

Open valve up and sww if there is gunk/buildup there, mine used to stick something awful . good luck

thedanned

Thank you all for the replies.

DJ99 and Targetnut, I went ahead and set everything back to factory specs as per the FSM and went ahead and pulled the battery cable to reset the ECU. I dont know if this computer is smart enough to have learned values or not, but I did it anyway. With the dashpot and throttle stop set the TPS reads within specs. The truck seems to run better overall and the throttle is not sticking anymore but the idle issue is still there.

Limon and Teuf: I went ahead and cleaned the bejeesus out of the TB while I had it off. Made sure there was no blockage or carbon build up anywhere. And I agree with you, that every single throttle bore I have seen seals COMPLETELY when shut.

I think my next step is to go down to U Pull and examine some throttle bodies. I will let everyone know what I find!

thedanned

Actually, what I should do next is check the adjustment of the Aux Air Valve as Targetnut has suggested. Looks like its time to read the FSM!

limon32

I could be wrong but I don't believe the aux. air valve is adjustable, I think it either works or doesn't and if it doesn't you get to replace the throttle body. I could be wrong, can someone confirm this?

abecedarian

The AAV can be serviced, i.e.: cleaned, but should not be adjusted unless you have the facilities to test and adjust it. On the up side, it can be replaced.

limon32

I didn't see a procedure for that in the FSM, did I just miss it?

abecedarian

Nope, you didn't miss it- service procedures are not there.
Though it can be taken apart, cleaned and reassembled, getting the valve adjusted properly through trial and error would take quite a while. Only recommendation I could give to this would be to count turns on everything your have to unscrew and re-assemble exactly as it came apart.

thedanned

I couldnt find it either. I think I may just clean it, maybe try and adjust it this week. Im waiting for the weekend to run to u pull and look at some other TBs.

DupermanDave

Is the silicone seal around the VAFM still intact? If you adjust the air/fuel mixture that will also raise the idle. But if this were the case, you'd smell gas fumes as a rich mixture. It's still a place to look. Previous owner might have tinkered with it.

thedanned

!!!!!!! I am running rich! I can smell my brand new cat working hard! And come to think of it, there is a self tapping screw point (the 'drill' part) sticking out of part of the VAFM, like someone was trying to fill a hole they created. Its not like they drilled a hole in the "airway" of the meter, its somewhere in the outer areas of the body of the meter. Ill look closer when I get home. Is the VAFM something that people tinker with? Ill search around for while. Thanks dude!

DupermanDave

It's something people mess with to "mod" the 22re to run a richer mixture to try and get more HP.

There was a post here with pics how to adjust the VAFM. I can't find it now, but I'll keep searching.

-edit-
well here's the post, without pics. https://www.yotatech.com/forums/f116...ng-maf-119680/

Seems the photobucket account went inactive.

thedanned

So here are a couple pics of my VAFM. Does this look like it has been futzed with? Notice the self tapping screw point sticking out of the round piece. The silicone seal seems to be intact.

abecedarian

The screw is sticking out of the plug that covers the idle fuel mixture adjustment. Normally, it's plugged with a blank, but it looks like someone drilled it out with the screw then inverted it so it would be plugged but easily removable.
Turning it in should decrease the amount of air that bypasses the vane in the meter, thus enriching the mixture, and turning it out should increase the bypass air thus leaning the mixture.

thedanned

Ok so I played with the screw (heh) for a little while, seeing what it does. Just as Abe said, in richens the mix and out leans it. When I pulled the plug, it was all the way in ie bottomed out. I then went all the way out, counting turns and seeing what it did to my idle. I am now twelve turns out (it is about a turn and a half from coming out) and it is idling at about 950-1000. So something still cannot be right here.

abecedarian

I wouldn't suggest you play with that screw unless you have an exhaust gas analyzer on hand to dial in the idle fuel mixture. Off idle, that screw has little effect on the mixture.