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Ok people, so after many months of frustration and pulling my hair out, I finally got to the bottom of my high idle problem.
Just to recap, my rig would idle at 1700 ish even after it was up to temperature. The only way to get it to idle normally was by physically closing the TB by hand or turning the engine off and restarting it. Sometimes if I blipped the throttle it would drop to 1000 rpm or so but climb right back up again after driving it again. I tried cleaning and testing my MAF, IAC, TPS and Throttle Body. Checked and double checked my vacuum lines. Lubed the TB linkage and rod, as well as researched until I was going cross-eyed but nothing would solve my high idle problem.
So what did I do you ask? Well I took the TB off again and really looked closely at the linkage and the throttle valve. What I noticed was that when I held it up to a light and looked directly at the clearance between the bore and the butterfly valve itself, as I let the valve close slowly, there was contact between the two surfaces just above the rod on the TPS side before the valve was completely closed and that contact spot would move up toward the middle of the TB wall as it closed all the way.
This caused the linkage to shift about 1/16" - 1/8" away from the TPS. Everytime I opened and closed the TB the rod would shift in and out because the throttle valve was hitting the wall of the bore and shifting out. I could actually feel resistance as the valve opened and closed while it was in contact with the inside of the bore. So I tried to physically restrict the rod from sliding back toward the TPS by holding it out and when I turned it, that way it closed completely all the way around the bore with no restriction whatsoever! So all I did to prevent the rod from sliding back was put a thin washer between the spring pack and the throttle body housing. IDLES PERFECTLY EVERY TIME NOW!!! Best of all it cost me nothing to fix it.
This is a real issue with higher mileage 3.4 V-6's and it regularly crops up after someone cleans out their TB.
Quite often the grime that was on the walls of the bore would create a seal of sorts between the TB plate and the walls and after the cleaning, this "seal" would be gone allowing the air to get by the TB plate. The reason there is this gap there now is due to many miles of use. The constant opening and closing of the valve along with vibration, wears a small groove in the wall allowing the air to get by. Usually this groove is on the left hand side of the wall when you're looking down the bore because of the return spring tension on the TB rod as it pushes the assembly toward the far side wall. Eventually the TB plate starts to hang up on the far side of the wall and can't close all the way anymore.
This may not be your issue as there could be a number of things wrong such as your IAC valve may have debris in it from when it was cleaned, or you have a vacuum leak somewhere.
Hope this helps as I know how frustrating this High Idle issue can be!
When my high idle occured I noticed the same gap in the butterfly valve in the opening of the TB. But I also noticed it was held open slightly by some kind of spring tension. It had some give to it. I believe there is a linkage on the backside of the TB (couldn't really see it without removing the TB) and it is controlled by the ECM to help with start-up. Once it warms up it closes as it should. So I didn't mess with mine. What worked for me was to remove the plastic air tube and leave it off, squirt 2 quick shots of MAF cleaner down the hole in front of the throttle plate and start the engine. It fired up and then died (no MAF signal), I did it again and the same thing happened, did it one last time and it stalled again. after 3 cleanings, I reconneted the Air tube and it fired up at idled @ 750rpm. Its been smooth ever since.
Why? My belief is that the IAC valve got jammed with carbon crud after spraying the TB with carb cleaner and the carbon drained down the IAC hole and dried on the pintle. What I did above loosened the carbon and allowed the engine to suck the crud past the pintle, clearing the blockage. But whatever the reason, it worked for me and it didn't involve removing the IAC or rebuilding the TB. Maybe someone can try this on theirs the next time it comes up. Sure was an easy fix.
I have the exact same issue. I noticed that the valve wasn't closing all the way as well. My solution was to add a spring to help close the valve. It worked perfectly but my throttle is stiffer now. I think I'll try putting the washer in. Thanks for the tip.
Ok people, so after many months of frustration and pulling my hair out, I finally got to the bottom of my high idle problem.
Just to recap, my rig would idle at 1700 ish even after it was up to temperature. The only way to get it to idle normally was by physically closing the TB by hand or turning the engine off and restarting it. Sometimes if I blipped the throttle it would drop to 1000 rpm or so but climb right back up again after driving it again. I tried cleaning and testing my MAF, IAC, TPS and Throttle Body. Checked and double checked my vacuum lines. Lubed the TB linkage and rod, as well as researched until I was going cross-eyed but nothing would solve my high idle problem.
So what did I do, you ask? Well I took the TB off again and really looked closely at the linkage and the throttle valve. What I noticed was that when I held it up to a light and looked directly at the clearance between the bore and the butterfly valve itself, as I let the valve close slowly, there was contact between the two surfaces just above the rod on the TPS side before the valve was completely closed and that contact spot would move up toward the middle of the TB wall as it closed all the way.
This caused the linkage to shift about 1/16" - 1/8" away from the TPS. Everytime I opened and closed the TB the rod would shift in and out because the throttle valve was hitting the wall of the bore and shifting out. I could actually feel resistance as the valve opened and closed while it was in contact with the inside of the bore. So I tried to physically restrict the rod from sliding back toward the TPS by holding it out and when I turned it, that way it closed completely all the way around the bore with no restriction whatsoever! So all I did to prevent the rod from sliding back was put a thin washer between the spring pack and the throttle body housing. IDLES PERFECTLY EVERY TIME NOW!!! Best of all it cost me nothing to fix it.
Try it out guys and maybe it will work for you!
Hey Swede, I stumbled on your write up about the washer fix after weeks of frustration with high idle on my '99 Taco. So I tried it and it worked! I joined the forum just to thank you (and check it out) for sharing, saved me alot of time!!
What size washer is recommended? I had to replace the piece of hose connecting to the throttle body. While I was in there I figured what the heck I'll clean the throttle body. As you probably know I have a really high idle. I would like to throw a washer on there tonight and see if it fixes the issue.
What all does one need to remove to get the washer on? Do I need to remove that whole unit or can I do it while it's all still attached?
The washer size (thickness) just depends on the amount the valve is offset or pushed over to the inner wall. If it's only offset a little bit the you need to file more material off the washer. If you have to move the valve a lot then you may not have to file at all. Other than that, just use a washer that has a big enough bore to slide over the rod and go from there.
Just wanted to say Thanks for this info! It took afew different attempts with washer thicknesses and fileing but it managed to fix my high idle issue! It was the only issue I had with my 3.4 swap and it was really pi##ing me off.
I have had this exact problem for months now and its driving me nuts.
If I pull my throttle body linkage towards the rad it immediately drops to normal RPM.
I tried putting a washer on the end of the butterfly shaft where the nut is located but I found this just caused the linkage to bind whenever the throttle cable pulls on it.
Does the washer have to be sandwiched between the throttle body housing and the linkage? As opposed to just taking the nut off the end and placing it there?
Had another look and realized my throttle body is totally different from yours.
The butterfly shaft is separate from the throttle cable linkage and connected by a small arm so unfortunately this fix won't work for me. It just binds up when I place a washer in there.
I thought about using a spring but since the linkage moves so much its hard find a spot to put it.
I'm almost thinking about using Bondo or some high temp silicone in the throttle body bore to fill in the material that's been scraped away and allow it to seal properly.
Really don't want to look for a used one since it may have the same issue and there seems to be several different kinds of throttle body for the 3.4.
Swede, you're awesome!! I've been banging my head against the throttle body for a week now. I cleaned the throttle body, IAC (which was a little dirty but not crusted up AND bench tested fine) and MAF sensor. I hunted for vacuum leaks, played with the TPS and even toyed with the idea of changing the upstream O2 sensor (the downstream was changed in the fall). I haven't put the washer in yet but I did pull the throttle linkage towards me and the idle dropped. Crazy! I joined just to thank you... and to offer you a few cold beverages of your choice if you ever get to Southern B.C.!
09-03-2012 | 04:22 PM
