2004 Gen 1 5vz-je Throttle Body Butterfly Valve Operations

Hello All,

My apologies if the answer is on the forum and I haven't found it yet, I have looked for a few days and figured I'd go ahead and ask for some help. If there's a thread out here for this and you could post it below, that would be much appreciated.

I bought a 2004 2WD Tacoma Pre-runner with the 5vz-fe about 2 years ago to haul things around as I do home remodels. I've used the truck to haul things or pull trailers locally as well as 5+ hrs on highway hauls. 2 weeks ago I took it on a run to get furniture and bring it back, it was about 5+ hrs each way. This was not the heaviest load I've hauled by any stretch.

On the trip, I noticed two things. First, the truck was downshifting a lot whenever there was a slight incline on the highway. Additionally, it was absolutely DRINKING gas. I averaged about 11 mpg on the highway.

Once I got home the poor performance prompted me to go ahead and swap out the spark plugs and coil packs, which I already had but hadn't prioritized changing yet. In the midst of this I took a look at the throttle body to see how it looked and noticed something unusual.

On the front of the throttle body there is a small wheel connected to the throttle cable. It would seem that I could turn the wheel about a quarter turn (or 50% or so of it's range of motion) before the butterfly valve in the throttle body even began to move. At the full range of motion the butterfly valve was only about 25% open. This made me wonder if the air/fuel mixture is messed up some some reason contributing to the poor power performance on the highway.

I started researching and noticed that there seem to be two different throttle bodies that are installed on the 5vz-fe engines. One that has a small diaphragm on the passenger side of the throttle body as well as some additional vacuum tube connectors on the top of the body. Mine doesn't have the diaphragm, nor the additional vacuum tube connectors. I believe my throttle body is factory because the screw threads on the body still have the yellow paint to mark their initial set positions from the factory.

This leads me to my questions:
- Is it possible for the throttle cable's set position on the wheel on the side of the throttle body to get out of whack? Such that the butterfly valve isn't opening as much as it should be?
- Does anyone know why there are two different throttle bodies in the 5vz-fe engines, and what the differences are between the two?
- Does anyone else have any suggestions on troubleshooting my poor gas performance?

Thanks so much to everyone in advance for any help provided.

Carl

 

Was your furniture load a High Load up above the cab even though it was light in weight.

That drops your fuel mileage fast as my mileage is between 10 and 12 mpg at best that sounds normal if your load is above the cab

Also head wind or cross wind will effect mileage in a negative way in a dramatic fashion.

Any Codes ??

Cables can stretch and start to break over time.

I had the floor break where the cable comes through causing some interesting things.

 

Dude I went through this same exact issue when I took my blower off. The difference(to my knowledge) is the position of the “wheel”. My wheel will turn counter clockwise as the cable wraps the other way and is pulled from the bottom. I can see our aic are in different spurs as well. The throttle cable brackets are also different to accommodate the different position. Not sure of the internal differences but I can confirm there are 2 different styles of tb. Also I adjusted my throttle cable and cruise cable so that if I barely hit the gas I have throttle response. It was sloppy before. Just don’t over adjust it so the butterfly valve is always slightly open. You want a tiny bit of play so the valve is always resting at full close.

looking at yours, you have a different style than mine. Let me see if I can grab a picture of mine today.

 

Hey Wyoming09,

No, the furniture was set very low, had two boxes maybe 30"high and the rest were under 10" tall. I had more wind resistance with previous trailer hauls. There was some wind indeed, but I checked the weather and it was similar to what I see on those long hauls.

Not sure on codes yet, need to take it to autozone or somewhere to pull codes for me, I don't have a code reader myself yet. If anyone has any recommendations I'd like to pick one up.

You had the floor break?! I'm sure that gave you lots of headache, what all was impacted?

 

Billson_,

How'd you decide where you wanted to call the stop point on your wheel? Just rotate it a little until you get close to seeing the butterfly valve move and then tighten it back down? That's good advice, I may give that a shot here and see what I get.

Thanks for at least confirming the two tb models. I was about to lose my mind looking at youtube videos for Gen 1 tacomas and they keep pulling stuff off that's not even on my tb, ha.

 

Sorry I misread your post. I was talking about adjusting the cable. I’m not sure why your valve isn’t moving when the linkage is being turned? Maybe something is loose on it? Have you taken it off and gave it a once over?

 

Gotcha. I haven't taken it off yet, I was trying to do more research into what was involved before I pulled it, which led me down the two tb rabbit trail. I'm going to try and dig around the tb a bit more this afternoon.

 

look at my sig, you have the Electronic Throttle Body (03-04) that was the "drive-by-wire" attempt for Toyota (also on 01-02 4Runner).

Explanations abound but simply this:

the pedal gets pushed, the APPS (Accelerator Pedal Position Sensor) tells the ECM how far you pushed it. The ECM then has the motor that is beneath the TB turn the butterfly accordingly. Then the Throttle Position Sensor (TPS) tells the ECM if that's true or not.

That "wheel" on the front is the APPS. It will allow the 25% opening when you floor it, called "limp mode" if there is ever any problems with any of the systems reporting back. This allows you to get off the road and either make it home or get a tow to have it looked at.

common problem with all the TBs is carbon build-up. when you go to clean the TB butterfly it then leaves a gap around the edges due to the wear over the years. @1997tacomav6 has a post where he sent out the TB to have it "rehoned" and a new butterfly put in by MaxBore (sp?).


regardless if your truck is anything but stock it's a wind sail for certain situations.

 

I had a 2003 gti that was drive by wire and idk if it’s the same but do not turn the butterfly valve by hand. If you do it will mess up the servos so I’d be wary about messing with it until you know for sure

 

More of a pain to remove the door and seat the lower dash panel to have access to weld a new piece for the throttle to attach to.

Thinking about it no more then what I need to remove for a Clutch Master Cylinder

Been a few years so far so good!

 

Yeah that's normal for that god forsaken electronic tb

 

Yep normal.

 

Just a follow-up for anyone finding this thread down the road:

Made the same road trip in the tacoma and hauled some furniture back in the bed. I didn't have the trailer this time, but wasn't driving unloaded. I noticed the downshifting again early in the drive out and decided to make the round trip sans cruise control. Got about 17 mpg on the highway. Seems like the issue is largely the parameters for when the cruise settings initiated a downshift.

Thanks everyone that chimed in on this one.