Lance

I'm trying to improve my mileage and noticed these ports on top of the intake. I've circled them in red in the attached picture. I'm missing one of the black "covers": Are they suppose to be attached to tube? Is missing a black cover, is that bad, lower MPG etc? My Haynes manual shows tubes running to some type of canister.

Thanks for all your help.

99 4Runner limited, with 3.4 auto.

rworegon

Depending on the emissions set-up, they may be used or not. On my 95.5, federal spec they are both capped with the covers shown in your picture. If one is uncapped and it's not supposed to be, it would likely create a vacuum leak letting unmeasured air into the throttle body and the ECU may respond by dumping in more fuel.

Are there any additional small ports that are unplugged that possible should be connected to this one? If not, put a plug on this one and see how it goes.

I see 'em capped here too...post 41, pic 3 shows it real good.
http://www.ultimateyota.com/index.ph...&topic=2241.30

RogueYota

Look like they are for an IAC....I could be wrong though.

rworegon

No, they do not go to the IAC on on the 3.4. The IAC is under the TB and has two coolant lines and a much larger air assist hose attached to it.

vital22re

iTrader: (2)

they are not used on mine and several 3.4 that i've dealt with. Maybe its used in the japan/euro market.

TheDurk

The Fuel System chapter in the FSM that covers the throttle body instructs you to blow out the orifices in the TB when cleaning the TB. The illustration clearly shows a compressor nozzle applied to one of these tubes. I know of no other usage for these. So I am declaring them as clean-out ports until someone comes up with a better story. I've posted this challenge every time I see this question and so far no one has come back with a better story.

Lance

Thanks for the replies. Mine looks the same as that picture, thank you.
(I see 'em capped here too...post 41, pic 3 shows it real good.
http://www.ultimateyota.com/index.ph...&topic=2241.30)

I recently had a valve cover seal replaced and I thought that something back there was missing. In the same picture near the back of the TB you can see a port pointing to the fire wall and a thread area for a bolt to the side of this port. With the missing black cap, this "void" and from the picture in the Haynes manual, I thought he forgot to install something during the service. The Haynes manual 92076 on page 6-3 under Emissions and engine control systems, illustration 1.3c shows a EGR Vacuum modulator in the void with two hoses going to those ports in question.

I don't have enough experience to gauge how accurate this manual is though.

TheDurk

I'd say you win, Lance. I don't think the 3rd Gen V6 for 4 Runners ever had a EGR system (not sure about Taco's), but that manual covers back to 1993 T100's. (I have that book, but never use it.) EGR hookup it is--but it's also a clean-out port for our purposes.

Lance

I'm thinking that the manual covers several models of the 3.4. I'm satisfied that my 3.4 didn't come with anything in that area.

Nelsonmd

This is a pretty sweet thread as I have wondered about those connections on mine too.

here is some other stuff I found about it:

https://www.yotatech.com/forums/f116...fe-egr-131562/

This shows the EGR hooked up to those ports.
http://arrc.epnet.com/autoapp/8682/8...EM_TESTING.htm

BigBallsMcFalls

those are just more ports available so the throttle body can be used in various configurations....or test ports