TexanTaco

So this weekend I was cleaning out the throttle body on our 4Runner and I decided to do the same w/ the Tacoma. For some reason I wasn't able to fully open the throttle valve on the Tacoma? I would say it opened about 1/4 of the way. I was manually opening the valve on both engines, but I could get the 4Runner throttle to open all the way.

I didn't realize how much dirt could get in there! I cleaned the MAF sensors on both trucks also, and they run great now.

GSGALLANT

When you say "manually opening", do you mean using the "lever" on the outside of the throttle body that the accelerator pedal cable connects to? If so, It's probably because the 2004 has a throttle control motor, accelerator pedal position sensor and a throttle position sensor on the throttle body. It's electronically controlled as opposed to directly driven from the accelerator cable. (I'm guessing that the Tacoma is the same as the 4Runner of similar years when it comes to throttle bodies... this may not be the case.)

It opening 1/4 of the way using that same "lever", when the truck is not running, is normal. It is a limp mode design that allows you to drive the vehicle home with some limited throttle input if the electronics fail.

I thought the 1998 4Runner was like that too, but I guess they changed the throttle body somewhere halfway through the 3rd gen 4Runners, because my 2002 is throttle by wire, same as your Tacoma.

mt_goat

I think the 4runner went to throttle-by-wire in 2000. Tacomas went to TBW in late 2002 or early 2003.

raydouble

01 Runner with throttle by wire here...........

TexanTaco

Yep that is how I was opening it, with the lever that the throttle cable attaches to. That makes perfect sense because on the Tacoma I noticed a wiring harness on that assembly, but not on the 4runner. Thank you for clearing that up for me! It was much easier cleaning out the TB on the runner because of that. What is the best way to fully open the valve on the Taco?

TexanTaco

I wonder why Toyota didn't change them at the same time? Well in any case, now I know why the 4Runner is easier to work on. I've noticed some other little differences between the 5vz's in both trucks.

mt_goat

I don't know, I think it was stupid to go to TBW. I'm glad I don't have it.

raydouble

Probably has to do with 4Runners being built in Japan and Tacos being built in Usa.

skjos

You have to manually turn the valve to get it to open past the 1/4 way position. Long skinny fingers help.

TexanTaco

What are the advantages (if any) of TBW?

This might be a stupid question, but if the Tacoma has TBW, does it have the same IAC valve as the 4runner? I don't see that valve on my truck, or I might be looking in the wrong place.

TexanTaco

Good point, but I wonder do the engines come from the same place?

TexanTaco

Do you mean push on the throttle plate itself? It didn't feel like it wanted to move.

raydouble

Good point, didn't think of that.

It has quite a bit of spring pressure against it, it will open.

GSGALLANT

Yes. I use the "lever" outside the throttle body to get the plate open 1/4 of the way, then I take the handle end of a rubber grip screwdriver to prop the plate open fully while I spray and scrub the throttle body.

mt_goat

I think all the 5VZ engines were shipped over. The TB may not be part of the long block though, I don't know.

TexanTaco

Ok now I know what to do next time!

Thanks for the help guys!

GSGALLANT

Advantages of TBW are that:

- It allows the ECM to control the throttle opening automatically when the vehicle has VSC and TRAC (if you want to call that an advantage).

- The electronic throttle control system talks to the transmission ECU to automatically reduce throttle during shifts (which is designed to reduce shifting shock).

- It allows the idle speed to be controlled better.

- It eliminates the need for a separate cruise control system. The ECM and electronic throttle control system take care of that function.


I think the IAC valves are different. I'm pretty sure you can't remove the IAC valve from the ETC throttle bodies for cleaning like you could the older ones (I've never actually checked, but I'm pretty sure).

Also, I'm pretty sure that all the things that affect idle speed (power steering idle up, AC idle up, cold idle, warm idle, auto transmission load, electrical load) are fed as inputs into the idle air control valve from the output of electronic sensors in the new systems, and not via individual VSV's like the older systems (again, I'm not 100% sure on this).

GSGALLANT

As an alternative, I think if you have the ignition to "ON" even with the truck not running, moving the "lever" outside the TB will control the throttle plate through it's full range of motion.

TexanTaco

First of all thank you for all the helpful info! I had planned on removing the IAC valve on the 4runner to clean it, but I need to buy a replacement gasket for the throttle body just in case. It's fairly easy to get to so I will work on that some other weekend. From what I've read the IAC can get very clogged up with carbon buildup, not good!

The Tacoma doesn't appear to have the same IAC valve so I'm not going to attempt to mess with any of that. LOL

TexanTaco

I'm gonna give that a try, thanks!