High idle due to butterfly shaft sticking (5VZ-FE Manual trans)

I have been having an issue where the shaft connected to the butterfly valve is sticking and will not let the truck idle under 1000rpm and in turn will not let me decel/engine brake. If i am going at any speed and push in the clutch the rpms go up as if i had the clutch still engaged, also at random times the rpms will fluctuate up and down as if i was engaging and disengaging the clutch over and over. I replaced the clutch and pressure plate 8k miles ago. If i pull the butterfly shaft linkage towards the dashpot it idles wonderfully at 700rpm, but when i blip the throttle it will not go back to that position and idles at 1000-1200rpm. i have a very clean butterlfy valve (no air gaps) and my IACV works properly. all vacuum lines have been checked, re-checked, and checked once more. this problem is very intermittent and i have been unsuccessful at replicating the situation in which it occurs(speed, temp, humidity). ive tried lubricating the butterfly shaft and that didnt work for very long and no other forum post has helped me with my issue. any input would be very helpful.

 

This might help. Read the whole thread for subtle tips and man vs auto t-bodies.
Seen the same "fix" on several Toy forums (5vz).

 

I apologize if this is the wrong way to reply, I am new to this whole "forum" thing, however i have thouroughly reviewed that thread, and like I said, ive scoured the internet on nearly every forum post and youtube video for a high idle situation with my engines specificity, and nothing has been very helpful, its mainly just dirty TB's or faulty IAC valves. I do like his solution a lot with the washer to fix the butterfly clearance but there is virtually no light passing through the bore of my TB, my issue is in the rotational movement where there is a spring-like pressure holding the butterfly barely 1/32" open, there also is some sort of surface contact in the rotating assembly that causes there to be a catch in between normal idle position and where it is being forced to idle at by that mysterious pressure(this occurs while the TB is on the bench and while installed in the truck so a vacuum leak is not the issue). I appreciate your input, thank you.

 

Well fine then.
When the engine is off, the throttle plate should be held slightly open by spring tension from the "throttle opener". It's the fellow dead center of the pic below with the small vacuum line. When the engine starts and vacuum gets above 6-7 inHg the diaphragm in the throttle opener will overcome the spring and the t-plate will close. This allows a little extra air flow for starting. If you pull the vacuum line off the opener and plug it (warm engine running) the RPMs should rise to 900-1950.
Maybe something is binding/sticking in the throttle opener itself?

 

I'll go and mess with the throttle opener and see if that does anything. thanks for the info!

 

would it be wise to spray a little brakleen in the throttle opener? from what ive read it does not leave a residue but im not sure if it is plastic safe. maybe the sticking problem i'm having is some gunk in the diaphragm.

 

I would be hesitant with the solvent and the plastic safe bit. Maybe as a last resort. I don't believe that little fellow is sold separate from an entire t-body.
There really should not be anything fowling the TO like happens to a PCV valve. How about repeated plug/unplug of the vacuum line (engine running) to "exercise" it, maybe observe it screwing up? Also check for full manifold vacuum on that line and see if the opener itself will hold vacuum with a vacuum pump. Any crud visible in the vacuum line?
I still would not give up on the throttle/shim thing just yet, maybe keep it on the back burner for now.

 

I'll give those options a try! hopefully they work

 

Once the truck was up to temp i gave the throttle opener a try and that just made things worse, its idling at about 1800rpm and when i push in the clutch to shift it goes up to 3000! i disconnected the battery to try and let the ecu relearn and after 30 minutes of going through the gears nothing has changed. one thing i did notice is that the upper radiator hose does not get hot or hard, radiator is full of 50/50 mix of Peak and distilled water from when i did the timing belt a while ago but there some rusty buildup. could a clogged cooling system cause a high idle condition?
P.S. the truck has never over heated, the highest ive seen the dash temp get to is just barely over the halfway mark and my ultragauge read 195*F

 

Can you still get down to normal idle speed by pulling forward on the throttle plate shaft?
Can you read throttle plate angle/value on the ultragauge? It should be "around" 10 deg at idle.

 

Yes if i pull the shaft towards the dashpot it idles perfectly around 700rpm, but when i give it some throttle whether it's from the gas pedal or pulling the linkage, it acts as if it has a detent in the shaft and gives some resistance before popping out of that position and revving up, but once the throttle closes it can never go past that "detent" to 700rpm, it just sat at 1100rpm. My recent idle is now down from 1800- after messing with the TO vacuum- to 1200-1300rpm. i got the engine warm and with a thick towel i opened the radiator cap and nothing spouted out, no movement at all inside the radiator except when i squish the upper hose. I am beginning to suspect that i have a cavitated impeller on my waterpump or my radiator is completely clogged and is somehow not over heating

 

Found a thread saying if i can move the shaft back and forth and have it go to normal idle, then the shaft bushings have gone bad. I highly doubt its a thing but do people sell parts to rebuild a 3.4 TB? that would be far less expensive and time consuming than trying to find a correct TB and then have it actually work properly.

 

I am chasing this anomaly (albeit with no real vigor) on mine for a few years. It's random low (as low as 250) and high (as high as 1600). My TB is a little different being that's it is an electronic version.

Now a question to pose. In the picture below, how "tight" is your return spring? Check for any bends or breaks in the coiled spring, does it fly closed like it wants to cut your finger off?

Just a thought to help it keep closed.

 

The return springs in mine look perfect and it closes with some force, i almost got my finger stuck in the butterfly valve when i was messing with the TB with the air tube off. im going to try the washer trick tomorrow along with finding an OEM thermostat because the one i bought was very different looking than the one i pulled out of the water pump. also everyone at the shop i was doing this at said to put the jiggle valve on the T-stat at the 12 O'clock position and a ton of threads are telling me it should have been the 6 O'clock position. but everything on my TB seems to operate properly except for the fact that it has a slight catch to it in the normal idle position.

 

I think 4cyl is 12 o'clock and 6cyl is 6 o'clock, there were a few posts about this this past week.

 

thanks for the info! anything helps at this point

 

Got a new muffler yesterday and it made the truck idle better and able to engine brake, old muffler was completely blown out. This seemed to be the fix.

 

In these situations I have had 85% luck taking it apart and putting it back together. Who knows. It's free and worth a shot. It's fairly easy to take the TB off and take it apart. The IAC screw's might get mad at you but everything else is easy. Strange it would hang up unless you have a bad mating surface somewhere

 

I took the TB off and removed the IAC which had a bit of carbon on the rotor and the throttle plate was spotless, no clearance around the bore and not even enough carbon on the inside to dirty a rag. Nevertheless I gave the TB and the IAC a cleaning and popped them back on the truck and the same old high idle still after a good 45 minute drive. Went to the muffler shop the next day and that fixed my engine braking problem and allowed it to idle around 1100rpm. Flushed the coolant and installed a new T-stat and that seemed to fix my idle. Thank you for your input Beau.

 

My 2000 V6 is in at the dealer right now for a few things like front end alignment and I asked them to diagnose the high idle. They reported back that the throttle butterfly shaft holes in the TB were worn and allowing air to leak in thus causing the high idle. So, has anyone found a source for rebuilt throttle bodies? They quoted me $1,400 for replacement, we can buy the Toyota replacement for $881, but perhaps there are rebuild units around, or a machine shop that can remove the butterfly, install a bushing, and reinstall the butterfly.