1997 Tacoma vacuum line question

Hey everyone!

New to this thread and relatively new to Toyota's as well. I have a 1997 Tacoma 2.7 regular cab that was imported from California (currently in Ontario) and the truck has 208000 miles and supposedly the motor has 160000 kms. I have read countless threads and have done tons of research but am having high/rough idle issues and some stalling.

The truck threw a cat code and TPS code so I did end up replacing both of those and the TPS did seem to help somewhat. Initially the truck had a very high idle and we noticed the vacuum line from the intake to the IAC had an excessive amount of vacuum in it so we actually pinched that off and adjusted the idle manually for the meantime. So i guess my first question is what is the exact purpose of that line?

Lately it has stalled twice on start up and occasionally on start up it can be a little rough but once it warms up its great or if its driven then shut off for an hour or so then driven again its fine. I cleaned the throttle body when I had it all apart and it was very dirty so I will be running seafoam using the intake method with the spray bottle to help clean it up since I dont know the engines real past.

Any insight or information would be greatly appreciated!

 

Also picture of the new Tacoma!

 

I would love that to answer the question at hand but unfortunately you distracted me with the awesomeness of your new Tacoma...

But seriously I don't know the exact purpose of that line but I know it's required because my truck acted funny too when I tried to bypass it.

Oh... And welcome to TW

 

Welcome! A stuck PCV valve or plugged PCV tube can cause excessive vacuum and a poor idle. Have you checked those yet? Nice truck, there are a few of us here who still prefer Toyota pickups in their original configuration: regular cab, hand brake by the steering wheel, crank windows and two sticks on the floor.

 

Ahahaha thank you! It's in great condition, excited to tie up some loose ends and really bring it back to life.

I have not checked the PCV valve or tube, I will do that today, thank you! And I have had a 2015 and 2017 Silverado before and i honestly enjoy this way more

 

Pulled the PCV valve and tube, tube is clear and valve still rattles but will probably replace the PCV this week anyways. Like i said i currently have that tube from the air intake cut off and it idles lower but it starts a little rough and there is some hesitation. But when i open that tube back up it starts without hesitation and isnt rough but it idles VERY high and just keeps climbing.

 

Leave the IAC tube connected. That is how the engine manages your idle speed. It should be fairly high at first startup and drop to ~650 once warm. If it remains high then you probably need to clean or replace the IAC valve.

 

Thanks for the info! When I had the throttle body off I tried to remove the IAC but the screws were so tight I couldn't get it off. I am going to run some throttle body cleaner and sea foam through the truck tomorrow but who know's if that'll change anything.

 

Wish I had a fully functional computer! Just went through some similar issues- took bunch of pics because the diagrams in the Haynes book of the IAC "open" and Closed were actually the same drawing for both and I figured they might be helpful to someone else in same situation......sorry I'm unable to post them right now.

I DO have suggestion for the IAC removal: hit it a couple times (a few hours or the night before) with some PB Blaster or similar penetrant spray. The more time it has to "penetrate' (soak) the better off you'll be. Having read a bunch of threads by people who had trouble w/the 4 small screws which attach it to the throttle body I didn't spend much time w/ a screwdriver -tho the suggestion has been made to use only a 'right-angle' screwdriver for leverage ability.
I removed t.b. and sprayed PB Blaster on those screws several times the night before I tried taking it apart. I used a smallish, fairly new ( sharp, grippy jaw teeth ) pair of Vise-Grips (NOT needle-nose!) w/ slight curve to the jaw opening. Use patience and be aware it won't turn far before you have to re-position- not much swing room. They will be in there _tight_! (I tried impact screwdriver on spare- no go.) Mine ended with minimal damage and I used a screwdriver, not vise-grips, to re-assemble.

BEFORE you start get a new 'gasket' for the iac- it's a dealer part and it's very unlikely to be re-usable.

Have plenty of t.b. cleaner, a soft and a firm toothbrush and some lint-free shop towels handy. When I got mine apart it took me a while to figure out what I was looking at and how it's _supposed_ to operate. The 'valve' opens/closes by means of a little semi-cylindrical door that 'slides' open and closed. Picture a custom-made "pocket door" in a house with a round room, curved just about like this: )

Don't know about yours but mine was basically immobile due to sooty carbon build-up. There's no way any cleaning of just the throttle body would have made it .
function again- manual cleaning was absolutely necessary. In fact, I had cleaned both my intake and the throttle body- looked shiny clean but inside all the little valves and peripherals -uh-uh.
Made HUGE difference in my idle speed.
Don't forget the MAF and the -damn, drawing a blank, it's another sensor, also located inside the airbox, sorry! Use ONLY MAF -specific cleaner and follow the directions to the letter. Don't touch the wires !! Those little babies cost a small fortune but your truck requires them to be driveable.

 

Thank you for your reply! Shortly after reading this weeks ago i ordered a new gasket and 4 new screws just in case. Got it apart and cleaned it and it did make a little bit of a difference. The plunger on the end, is it supposed to move in and out (open/close) or rotate (open/close)? Still have an issue of the idle climbing when sitting in park at idle but trucks running better and is better on start up forsure.

 

Also few updates on how the trucks looking!

 

That line you pinched is the inlet for the idle air control valve. At idle it should have lots of vacuum as it is all that feeds your engine when the gas pedal isn't being pressed. You should see about cleaning your idle air conditioning trol valve, maybe it is stuck wide open causing high idle. Also is your engine reaching operating temp, it won't drop idle all the way down until it gets to 186°

 

I would suspect a worn throttle body first. Push in on the nut that holds the cable pulleys slightly and with you other hand open and let the spring close the throttle a few times and see if it is "normal", then pull out on it and it again and see if it "sticks". If the throttle plate does not center itself in the bore every time odd things happen. There is excessive air passing the throttle plate and the TPS (throttle position sensor) is telling the ECM that you are NOT at idle, the IAC (Intake air Compensator(sp?)) is trying to meet the screwy conditions and could be maxed out in its range of adjustment. This is a system of multiple components.

 

you're quite welcome, hope it was helpful.

...."The plunger on the end" : sorry, I'm having a little trouble visualising a "plunger"- can you give some additional detail, please?
...if you are referring to the moving portion of the valve (which I likened to a "pocket door"), it rotates open/closed.

 

Yeah that's the part im referring to. I no longer have that line pinched off and i have cleaned the IAC, everything seemed a little better but tonight i just threw a P0505 code, so looking like i may need to replace the IAC?

 

When you cleaned the IAC did you remove it from the throttle body? If you left it on you most likely washed a bunch of junk down into it. You have to completely remove it and replace the IAC gasket in the process.

If you did remove it and you got that code, then yes you probably need a new one.

 

Man, what a beauty!

 

.....possibly....the IAC is integrated with numerous other components that affect your engine control system(s).. The p0505 is a 'generic' code -it indicates a problem with the idle air control _system_ , which _could_ be a bad IAC valve BUT could also be a bad temp sensor (aka " ECT" for Engine Coolant Temperature sensor), or bad wiring pigtail, or ECU to mention just a few
Speedytech7's comment re: engine operating temperature is spot-on. FWIW: he seems quite knowledgeable regarding our Tacos- I don't know if he is/was a Toy tech but he's a pretty sharp cookie.
Glamisman has a point as well regarding worn throttle body.

Rather than throwing parts at it without knowing for certain the part you're replacing is bad start with the 'easy' stuff: test electronically (FSM or even Haynes manual for resistance/ values and a digital volt ohmmeter are necessary equipment here) and/or mechanically (vacuum pump, visual inspection, bench test). The FSM has a troubleshooting 'tree' -follow it step by step.
If you get to the point where you need to pull the throttle body to test the IAC be sure to get a new gasket from the dealership prior to disassembly. Clean thoroughly with toothbrush and throttle body or carb cleaner and shop towels untiil the valve (actually resembles a sliding pocket door) moves freely.

It can take a while (days to a couple of weeks) after cleaning throttle body/replacing parts/etc for your ECU to 'relearn' and idle speed issues to settle down.

 

What fender flares are those? OEM?

 

Thank you!

Yeah I have pulled the IAC and cleaned it and replaced the gasket and got 4 new screws as well. So far it seems a little better, haven't had many issues lately regarding the idling and starting. I cleared the code and going to wait and see if it comes back, if it comes back ill do some further digging to see whats going on! Thanks for all the info!

I believe they are OEM but i know bushwacker makes ones very similar.