91Toyota

My truck has been driving me crazy. In an attempt to fix it I have been over revving my engine (rev limiter)...and I want to stop really bad...but its driving me insane. I was told that it is a vacuum leak. I have sprayed starting fluid ALL over everything and my engine still just surges and doesn't do anything. So, what can cause this? Can I just start replacing parts? I have been thinking my TPS but I'm not sure. My idle screw is ALL the way turned in. Thanks for your help and patience.

thook

You know what, I had a vacuum leak around my cold start injector. Usually, starter fluid or an unlit propane torch would reveal a leak. But, I guess it's not a foolproof method because neither trick worked.

With your idle screw turned all the way in, the idle is supposed to go down.....of course. In the FSM, the test procedure for inspecting the auxiliary air valve (located in the belly portion of the TB) is to check that the idle does indeed drop when you turn the idle screw in. If yours is not doing that, the valve is what I'd blame. Of course, refer to the FSM for the exact procedure.

I don't know what that would mean in terms of repair as I've never had to deal with it. I do know you can take it apart and clean it, blow air through, what have you. But, if it's just plain bad, I don't know if the TB must be replaced.

Run a search on it. Even try the term idle air control valve.

91Toyota

Thats thook! I looked around last night and I found whats called an air auxiliary air valve and that could be the culprit. I am going to take it apart and see what I find. What else could be a culprit?

thook

With your given symptoms, I do believe that's it....if you understand how the thing works.

thook

Here's a link I found:
https://www.yotatech.com/forums/f116...51/index2.html

There are more, though.
http://www.toyotanation.com/forum/sh...ad.php?t=52117
http://autorepair.about.com/library/a/1/bl297.htm

DCYota

Have you taken the TB off yet to check for carbon build up? Sometimes on these trucks, massive amounts of carbon get gunked up in the throttle body, the intake, plenum, runners, etc (the infamous "black goo" problem that many have had)....it involves removing the upper intake and plenum. That can cause idle problems as well, and you'd never find that with starting fluid or propane Some people go so far as to take it all off, go to a machine shop and have them hot tank it to clean it out, then reinstall. I've heard great things from people after doing this as far as how the truck runs.

Seems to me that's the most likely culprit if it's not your IAC valve or related parts. If you stick a paperclip in the diagnostic terminals (TE1 and E1), and the idle audibly drops down, then your TPS is functioning as it should.

Have you tried that yet to rule out your TPS as one of the culprits?

91Toyota

Not entirely sure how it works. Is it the same thing (or attached to) as the butterfly thing/coolant temp sensor? A pic would be really nice!


Yes, I have, and I cleaned it so it should be alright. I cleaned it about 3k miles ago. That is a GREAT idea...I am going to do that. Does it have to be warm to do the test? I'm going to try it cold...thanks.

91Toyota

We can now rule out the TPS! When I jump those two terminals the idle jumps down...which is good. So, where is the Auxiliary Air Valve?

dcg9381

It's on the throttle body.

Look, you have 40-50 psi on cylinder 3. You have a *significant* problem.

Best case, a head gasket... that's the good case!

91Toyota

lol...I love you guys. Next person who says I have a head gasket problem I am going to come to there house and kick the living hell out of them.

NO, it does not have a head gasket problem. It's had 40-60 psi in that cylinder for 4k miles. I replaced the head gasket 1k miles ago, and I have an idling problem. Does not LOSE antifreeze. No antifreeze in the oil. NO signs of a head gasket. Its NOT possible.

It used to idle at 500rpm just fine, you can't tell that you have a bad cylinder...well sometimes.

Yeah, everyone says it's on the throttle body but where? What the am I looking for? I have no idea what it looks like? It is an "AIR" valve so I am assuming it is not the piece of crap below the butterfly. Where IS it????????

91Toyota

bump for quick response!

abecedarian

I'm just stabbing at it so...
Connect a vacuum gauge to the engine / intake manifold and get a good reading of the engine vacuum at idle. If the needle 'flicks' around or does not read very high ( should be at least 15" ), #3 has probably got a stuck or bent intake valve which is causing it to not close completely. This could cause unburnt fuel/air to be pushed back into the plenum which will affect idle stability AND could cause the low compression on #3.
There: two birds, one stone.

ssupercoolss

up and down idle. i had the same issue. turned out to be the aux air valve. it had an rtv bugger stuck in one of the lines which wasnt letting coolant flow to it, so the valve thought the truck was cold all the time. heres how you determine if its related to the aux air valve. take off the black hose that goes to the throttle body. just inside the opening you will see 2 or 3 little holes. take a piece of duct tape and cover them up. replace intake hose. start truck. keep in mind, with these holes closed you will probably have no cold idle, you will have to give it some gas. remember, the duct tape is a temporary solution. dont want that stuff getting sucked in to the intake.

thook

Here's the FSM page on the aux. valve.
http://personal.utulsa.edu/~nathan-b...35auxiliar.pdf

And, this is something I've run across recently:
http://www.autoshop101.com/forms/h21.pdf

It would be good to read the whole thing, but pgs. 6-9 refer specifically to air valve. If you could get an idea of how the system works, you should be able to figure out what's wrong.

91Toyota

I had a valve job done to the head. That's why I don't think it has anything to do with it. I will connect a vacuum gauge to it though and report back.

Ah, I see what you are talking about. That is a good idea and I am going to give that a try. What exactly does covering up the holes do? I have seen them before but I don't know what they do. Thanks!

Thanks! I am going to look those over right now.

91Toyota

So what does it mean if it doesn't run at all when I put duct tape over the hole? I am confused. I will try it again but not sure if it is going to work.

thook

Is your idle screw still turned all the way in? If so, you're not getting enough air in the intake.

Before I go any further, I'm curious. You are the fellow that had no dashpot set screw at one point, right? IF that's correct, in the thread posted with the pics, I'd noticed you had no throttle stop screw, either. Am I correct? Are you the fellow?

thook

Say, can take a picture of your throttle body? I'm not sure what design you have and need to know if yours has a throttle opening valve.

91Toyota

I'm not sure if I even have a throttle stop screw. I did not have a dash pot screw either...so I guess I am that guy. O.K, I will take some pics of my intake. I have one that I took of it apart. Should I take more?...here it is...

thook

Where's those pics of just the throttle body itself....not the entire intake? The ones where you were showing the screw missing?