JohnVH

on the V6's there is something you can adjust for that cool idle rpm.

Mine too takes a good 10-20min to hit the normal idle of 8-900 rpm, as most of my driving is around town, I hardly ever hit that number.

thook

The bimetal version is heated by, yes, a current supplied by the circuit open relay switch and ambient air temperature......not directly by coolant as with the thermal wax version. So, year of the system is certainly regarded. Besides, the bimetal versions are real prone to the element that closes the gate simply wearing out (metal fatigue) and no longer responding to temp's properly.......which can't be fixed. So, you just have to get another one. On the other hand, the gate itself can clog with carbon debris. That can be fixed, though.

Have a read, folks.......
http://autoshop101.com/forms/h21.pdf

You are right about the thermal wax valves. There's a lot more success with restoring those.

thook

I have a '92 V6. I don't know of any adjustment that can be made that will properly affect the cold idle. The IAV can't be adjusted in any way, so what else is there?
There's the idle bypass screw, but that shouldn't be used to adjust the idle until the engine is warm and the IAV is closed....ie, "curb idle adjustment".
Then, there's the throttle stop screw, but that affects throttle opening at idle whether the engine is warm or cold. As well, there's a definite specification for the throttle valve opening....IOW's a definition spec for the stop screw.
If you want to mess with any of that stuff, it's not really the proper way to address the problem simply because it's not going to have any effect on how long the IAV stays open......which is the problem. Unless it's the coolant sensor or the thermostat. But, with the coolant sensor, if it's going bad, you'll have more problems than a prolonged cold idle speed.

JohnVH

search, you can adjust the cold idle settings on the TB

thook

I'm not going to search, John. I just posted a link from the Toyota technical training site explaining how the induction system works. Any and all settings on the TB are for warm/curb idle adjustment to be done when the engine is warm and the IAV is closed. Anyone wants to do something different and dumb is their choice.

JohnVH

dumb, haha, at least you can spell. ( maybe it was spell checks help )

thook

I don't use a spell checker. I tell you what, though. For sake of curiosity, I did run a search to see what people are up to. Maybe it was my not using the right keywords, but I didn't find anything in reference to adjusting cold idle on a V6 with a thermal wax valve. Since you seem quite positive in your assertions, maybe you'd care to supply me with some good keywords? Then again, maybe not since you can't remember what "it's" called. Fair enough. I don't always remember terminology, either. So, if you happen to run across anything referring to the subject, would you care to shoot me a PM with a link? If I read the reference and find I'm wrong, I'll admit it right here in this thread. But, if I read and can point out all the things wrong with the idea and procedure, I'm gonna post that instead. Deal?

thook

So, lemme guess.........you're referring to this?:

https://www.yotatech.com/forums/f116...cation-110754/

Did some digging with your username. How 'bout that?

What's referred to in the pic and in the Haynes manual is the idle bypass screw and the procedure used in the illustration is testing for IAV operation......not to adjust cold idle or the IAV. When the bypass screw is fully screwed in while the motor is idling cold and high, the idea is that by shutting off the only other passage for air.....which is the idle bypass...aside from the IAV that should, at that point, be open......and aside from the opening of the throttle plate that is dictated by the position of the throttle stop screw or the throttle opener (in the case a/t equipped vehicles)..... the idle should make a notable drop....BUT....not so noticeable as it would be with the engine warm and the IAV closed. In the latter case, the engine should nearly die, if not die altogether from lack of air flow. This comparison in idle RPM indicates ONLY whether or not the IAV is operating as it should. If their is no difference in any case of RPM drop, it is assumed the IAV is not functioning. A good indicator would also be if the engine has reached operating temp and the engine is still idling too high at cold RPM's or if the engine will not reach cold RPM's though the coolant temp is still low. That is, provided one is sure there are no vacuum leaks.

Now, TNRabbit does refer to a "cold idle adjust" in a pic he supplied, but that pic is no longer shown. I know TNRabbit. Like any of us, we do make mistakes and TN may be mistaken. Can't say for certain how, though, since I can't see the pic. Maybe I should just shoot him a PM and ask? Hmmm....

4wd4fun

cold idle speed is controlled by the valve under the throttle body- it lets air around the thrttle plate when the engine's cold so causes a high idle speed like a carb requires you to press hte throttle down before starting and has a cam that blocks the throttle open and the choke restricts airflow so more fuel is sucked in.

TinMan

I've got th post 89 TB(straight). Thi has turned into a goo read though.

Thanks all

toystoplay

There is a lot of good info here! I may just be able to correct my problem. I've learned a lot.
This seems to be a helpful community and with knowledge wow!

Keep posting,


Thanks

thook

So, I'm PM'd TNRabbit, and he sent me a photo of the throttle opener and calling it the cold idle adjustment. So, this is where we'll have to disagree or explore the idea further. Either way, here's what the FSM has to say about throttle opener adjustment:

http://personal.utulsa.edu/~nathan-b...93throttle.pdf

On pg 238, it gives a procedure for inspecting and adjusting the throttle opener. Just as I thought, the procedure is done with a warm engine. I don't know where TN gets the idea it's for cold adjustment. As well, this adjustment still has nothing to do with IAV operation. Furthermore, there is no throttle opener on m/t vehicles. Only on, again, a/t vehicles. So, even if it were for cold idle adjust (and, it may be), it does not apply to 5spd engines.

JohnVH

no thook, not that, I have not had time to find it back yet, but I will. It has coolant going through it or something to that effect, so its temperature controlled, and adjustable.

thook

Isn't this what I've been saying all along? Yes, you can manipulate TB settings to alter cold idle speed. But, when you mess with those settings, since they are meant to be done on a warm engine, you also adversely affect warm/curb idle. So, again, the cold idle problem is not addressed.

thook

Okay. The only place on the TB that has coolant going through is the IAV. The thermal wax version, again, is not adjustable. The older style/bimetal is, however. The opening of the gate has an adjusting screw, but that's not pertinent to the original topic since V6's do not have them. As well, coolant does not pass through that valve gate.

thook

So, I thought about it some more and gave ol' TN the benefit of the doubt. I figured I might be mistaken/remembering incorrectly about how the throttle opener functions. You see, there's point at which the throttle opener is engaging the throttle linkage/set screw and a point at which it disengages. I thought, well....maybe the TO doesn't disengage the set screw until the motor has warmed up and idle has slowed down increasing the vacuum draw on the TO thereby disengaging it from the screw/linkage. So, I went and checked it. Just as I thought..........once the engine is running, the TO completely disengages the screw and therefore adjustment of the screw has no bearing on the opening of the throttle plate during a cold idle.

4wd4fun

the throttle opener / dashpot keeps the throttle from closing fully so theres no backfires during shifts. thats why it touches the throttle with the engine off and pulls off once its running.

thook

I'll keep that in mind. Thanks.

4wd4fun

oops.