thefreqofnature

I've been researching this for over a week and did some reading on the FSM and I still can't figure it out.

Backstory...
Its an 88 4Runner 3.0 5speed with about 300K miles. I've beed doing some work on it getting it ready to smog here in california. Belts, hoses radiator flush, that kind of thing.
I took off the air intake at the throttle body and found that its cracked so bad on the underside that I had to replace it. I found an air intake from a 93 for $7.50 at my local pick-a-part and it works well. I've checked all vacuum tubes and they seem ok.
While I had the air intake off I sprayed a bunch of carb cleaner into the throttle body and on to the throttle linkage and associated and surrounding parts, including the dash pot.

The engine is strong despite the high mileage and runs well, burns no oil and doesn't leak. Its a great truck!!

Problem...
If I start it in the morning when cold It will idle high at first then gradually reduce the rpm's to the correct idle, about 800 +/- 50 as it warms as it should
If I start it when its warm it will idle at about 800 like it should.
But, if I drive it around the block or keep the rpm's over 2500 for a little bit it will idle at about 1200 and will not go back down.
If I move the throttle linkage by hand it will return to 800 and idle there as it should.
Or, if I turn off the ignition and then turn it back on again it will idle at about 800 like it should.

My thoughts...
At first I thought it might be the dash pot staying out a little but I dont know how turning off the ignition would make that change.
Then I thought it might be the TPS because I imagine some carb cleaner went down the hole in the bottom of the throttle body.

I've removed the TPS connector when its idling correctly and the RPM's increase to about 1200 or so then will reduce back to about 800 when I reconnect it.

Could I have damaged the TPS with the carb cleaner?

Could I have damages the dash pot with the carb cleaner?


What do guys think? Thanks for your help!

MudHippy

It's possible. Since you aren't supposed to use carb cleaner on them.

thefreqofnature

Hum...?!? How did I miss that?!?

I wonder it all TPS's are the same for the 3vze?

Well, I'm off to the pick-a-part tomorrow morning to get a TPS.

thanks Mhippy

MudHippy

88 had a different TPS than 89-95. That's the only difference. That I know of. But yeah...that might be something to consider. Considering...you have an 88. And they're totally incompatible with each other.


Oh BTW...did you know the 88 3VZ-E only had 145 HP? Not the 150 HP of 89-95 3VZ-Es? But why/how? What changed to make 5 extra HP? I just solved that riddle finally. Just yesterday in fact. After nearly a decade of searching and wondering. Now I officially know EVERY single difference between the 88 and later years. Of which there are many. I'm having a nerdgasm contemplating the extent of my 3VZ-E wisdom. And it feels SOOOO GOOOOOOD!!!!!


And no...I'm not telling. Not yet. Gotta savor it a little while more. That and I haven't had the chance to make the proper measurements to prove it yet. After which I'll undoubtedly be starting a new thread just for bragging rights....I mean to help expand the breadth of free to the public Toyota knowledge....rather. Like I'm not that egotistical...when I really am!


EDIT: The suspense is killing me. So I'm spilling the beans. The 88 3VZ-E has shorter camshaft lobes(not sure how much yet, enough that it's easy to see by eye though) and looser valve clearance specs(+.003" In / +.002" Ex) than later years. Hmmmm....I wonder if that makes any difference for HP? < HINT...HINT.

thefreqofnature

Yup! I found out what you already know. The later model 3vze TPS is different than the 88 3vze. $3 wasted. Well not wasted, Now I know.
The throttle body is a little different too, so I couldnt use the dash pot I found.
It's very hard to find 1st gen v6 parts around here. The pick yourself yards dont have any and the 'full-serv' (?) yards want top dollar.


Awkward Wisdom is a funny funny thing. LOL


We can wait... Go ahead and savor. Its not like we could be out or anything. You've earned it, I'll bet its delicious.

That's a great rebuilding tip!! maybe? I don't really know
Thanks for your help Mhippy, its great to learn and have fun too!!

MudHippy

It might be. If you can score a pair of 89+ camshafts for cheap. New they'll run you 2/3 the price of having the 88 pair reground for a ~ 45 HP gain. So I don't really know either...


And yeah...I do get a little overzealous sometimes when it comes to talking Toyota's. Actually...quite a bit...and often. But don't mind me.

thefreqofnature

BTW do you happen to know anything about the Thermo Wax Valve? What's it do? Anything to do with idle? Can it be replaced? Rebuilt?
Oh, and what's the hole in the bottom of the throttle body, just before the butterfly?

I know you know!! Stop savoring! Spill the beans!!

Thanks again

MudHippy

Oh that damn thing. It opens and closes when the engine/coolant heats up/cools down. It opens and lets more air past the throttle when it's cold, which is why the idle speed is higher when it's cold. And lower when its warmed up, and the valve is closed.


I've never had to mess with one. All mine still work fine. There are no parts to fix them that I know of. Supposedly they're adjustable, to some degree. But there shouldn't any reason to ever need to. I heard a guy here mention how he adjusted his once though(so he says).

thefreqofnature

I'm still working on this...

This morning I went to start the 4Runner. It starts well, idles high, then drops to about 800 rpm +/-.

When I drive it down the road and come to a stop. It will idle at about 1200.

What I did different today is that at the stop when idling at 1200, I blipped the throttle to the floor for a split second and to my amazement the idle dropped to 800 +/-

Still not sure what the problem is but this is new info...

thanks for your help!!

MudHippy

It sounds almost exactly like the high idle issue I chased around for months after buying my 90. Just about lost my mind on it. Then one day I was messing with the air intake tube and found 2 hose clamps on it that the PO forgot to tighten all the way. The looked tight. So I never checked them. And sure enough after I tightened them up, the engine started idling correctly. I was like "you idiot... that's the first thing you should have checked...NOT THE LAST!". DOH!

voiddweller

Mine was doing that, took the throttle body off and found the coolant bypass inside it was clogged.. Cleaned it out along with the spring mechanism and stuff, worked like new after

thefreqofnature

I did replace the air intake tube because the old one was cracked.
I took them all off and cleaned and replaced them. I know they are fine but I'll check again. Thank You.

thefreqofnature

I was wondering about the coolant bypass thingy on an earlier post. All this trouble started when I drained and flushed my radiator. I'm fearfull of trying to remove it cause of those old screws have never been off.
Thanks for the input!!

88MemphisBlues

Does the throttle return spring have a good feeling return to it? One of the first things I did after pointing the finger at my own IACV was when I found a TB in a junkyard, I completely disassembled it to see for myself the inner workings of it without having to experiment on my own TB. (EDIT: I got lucky finding an 89 V6, because Toyota began backtracking, it seems, with corrections to design and the later V6's had different TB's, to include replaceable IACVs or that were simply bimetal in nature.) I wonder if your throttle return spring could be replaced, as that seems it could be an easy/cheap thing to do. On that same note, I found before replacing my own TPS, that its own return spring was very weakened, in fact it wasn't even returning it to its original home position which uses the TB plate as a backstop. I modified the spring by pulling it through it's own catch slot by a quarter inch, and then reattached it to the same spot. This certainly aided in its own return spring strength, but it was afterwards I discovered the dead spots with my own volt/ohmmeter and knew it was going to be replaced anyway.

It sounds like if you blip the throttle and it returns to true idle, something is going on with drag on your throttle cable's return, or the TB plate's ability to close successfully, or with the same return force every time. Especially after the motor expands with its own heat....

(2nd edit: could the throttle cable be lubricated in some way, with some tri-flow or something equivalent?)

thefreqofnature

When I turn it on in the morning, it idles high when its cold. As is warms it will return to the correct idle on is own.
Also...
When it high idles after is warm, I can turn the car off and back on and it will return to the correct idle on its own.

The return spring is very strong, I dont think that is the issue.

So right now I'm baffled.

I'm going to jumper the fuel pump and see what I can discover? LOL!

Thanks for your reply

voiddweller

Did you try thoroughly cleaning the bypass passage through the tb yet? I stuffed with the same problem and that's what solved it

88MemphisBlues

To piggyback on what voiddweller just asked, but specifically remarking on yours above, you could remove the TB and flush that channel out without removing the screws to the IACV cover plate. You must absolutely remove the TPS though, no point in putting liquid anywhere near the TB without removing the TPS as it's crucial to keep that guy's internals from getting soaked.

Although... if you've gone that far you might as well try to open it so you can visualize the before and after a good cleaning. Using boiling water from the kettle to clear out that passage, and you'll be able to see the valve close on its own due to the heat.

I've also wondered if the coolant flow to and from my own valve is somehow impeded, but not blocked. There was a youtube vid that i recently saw some liquid gasket applied to a water pump broke off and occluded the manifold feeder line to the TB, thus keeping a 22RE in cold idle the whole time, though there was no report of engine temps above normal.

Regardless, with a 6 dollar sheet of make your own gasket, you could easily take the TB off and on again troubleshooting this. I know, I've had mine off three times in the past month looking for my high idle issue and the gaskets have worked well (being I've tested them all afterwards with carb cleaner and there seems to be no discernible leaks at this junction.)

88MemphisBlues

Though as an afterthought I'd add that knowing you can simply "blip" the throttle while driving corrects this high idle issue makes me want to dismiss the IACV problem it can classically give because it's dirty or the coolant line is clogged. Blipping the throttle wouldn't fix this... unless blipping the throttle is creating enough coolant flow pressure to sweep past some clog in the line that was keeping the TB coolant line temp lower than needed for the bypass to work.

Either way, cleaning IACV and its coolant passageway (and its lines) out is excellent maintenance anyway.

88MemphisBlues

Did you ever figure this out thefreqofnature?

I'll include here what I posted in my original thread having a high start idle problem that only creeped up after "warming up," but if TLDR; it truly was that I either had air in my IACV passage (within the TB) that I couldn't get rid of or that my return coolant line was clogged and impeded the flow, both those problems were solved by a hand vacuum pump pulling fluid through both routes.

long: Wow. It may have been a plugged return coolant line after all. I borrowed a one man brake bleeding kit, which is just a glorified vacuum pump for any old use, and disconnect the coolant return behind the throttle body.

I then used the vacuum to pull fluid from the block supply and the throttle body to make sure it could flow (rear side of engine.) Check. Then I put the hand pump vacuum on the return side, which would pull the fluid the opposite way from which it would normally return to the Y shape pipe the firewall heater-core return it is shared with. I started pulling fluid and there was a distinctive resistance that was quickly and easily overcome. I figured it might be because I was going the wrong way in the way it was suppose to flow. I got my fluid after only a few pumps but there was a lot of particulates in the coolant. There wasn't a plug, per se, but there certainly was a bit of large black flakes. I took out a half-gallon of fluid this way, which is what it took to get the coolant completely clear of black flakes at any given sample. I primed the coolant as close to the end of the hose as I could and did the same with the TB coolant exit. I attached the two quickly and made sure I replaced the lost coolant on the part of the driveway that slopes 45 degrees, making sure the radiator cap was the highest point, by maybe 4-5 inches at that slope. The radiator fluid didn't seem to move, but I noticed my reservoir was almost completely out, and I was certain it had been topped to the full line. I of course was attempting to refill the coolant after connecting everything with the truck running, and it did the age old thing on the first crank after trying this; idling at 1000 if just north a bit. The throttle screw had been all the way in this whole time and after a few minutes of running watching the coolant, the truck started to idle down, which it had never done before since I've owned it. It took three full turns of the idle screw to get it back up to 800, and only driving it half a block I had to get out and back out the throttle screw another full turn (putting it at about 4 full turns from bottomed out, what I think I've read as the stock position for the 3VZE.)

Got back home and she was idling at 800 like I had set her on the quick test drive. Update: the next day test crank and hour drive, all from an overnight cold start yielded perfect results. The truck is running better than it ever has since I bought it before New Year's.