Idle fluctuation 4age

[dickhead]

Hey, anyone know what causes the idle to fluctuate? Have a 4age turbo, base idles at 800rpm but when you've been giving it a bit the idle starts fluxuating from 800 to 1600 continuously? I dont know if thats normal or not?
Cheers

[z0ton]

My ae82 does that. I think mines something to do with the vacumn hoses being around the wrong way...

[ezy10s]

I find the wax idle up unit on the bottom of the throttle bodycraps out occasionally creating the fluctuation- try swappiong on another one to cure it.
Of course this is only one possible problem- but if you have another 4AGE throttle body then its one that is easy to fix.

[andyztouring]

Clean the inside of the throttle body where the butterfly is mounted,get it spotlessly clean,has fixed 2 of my car,cheap and easy.

[CAMB01]

check for air leaks

[Crucible]

Make sure your coolant level is ok because that will give the same problem also.

[toyrota mota]

This happened to my ae82 it was corsed by the coolant lines in the throttle body getting all rusted up and blocked. I just got a not rusted TB from a wrecker and that fixed it.

[l1ttle_d3vil]

or try winding the idle screw down, my car does that if the idle is set too high.

[repowered]

i had the same problem, when i got the timing done it fixed it, but is still idling high aye

2.2K hot and 1.1K Cold - im guessing its got vacum leak somewhere?? i had a bit of pipe to the ear and moved it around afew places couldnt hear anything sucking.

cleaned out the inside of the TB, cloth was abit black afterward....made no difference.

will check the Round wax thing. Got spare 4age so will check if that has it on.

EDIT pics:

http://homepages.slingshot.co.nz/~jimco/images/Vacum_lines/Image052.jpg

http://homepages.slingshot.co.nz/~jimco/images/Vacum_lines/Image054.jpg

http://homepages.slingshot.co.nz/~jimco/images/Vacum_lines/Image055.jpg

http://homepages.slingshot.co.nz/~jimco/images/Vacum_lines/Image056.jpg

http://homepages.slingshot.co.nz/~jimco/images/Vacum_lines/Image057.jpg

[Stealer Of Souls]

I've been told that if the TPS isn't set correct it can cause hunting idle.
Another way to check if the cold idle valve is shagged. Take off the intake and when the idle is hunting you can stick you finger over the big round hole at the bottom of the throttle body just in front of the butterfly. If the hunting stops then it's quite likely that valve is shagged.
I've killed several cold idle valves. They don't like the coolant getting hot... I found that anything above three quarters on my guage starts to kill them.

[repowered]

I've been told that if the TPS isn't set correct it can cause hunting idle.
Another way to check if the cold idle valve is shagged. Take off the intake and when the idle is hunting you can stick you finger over the big round hole at the bottom of the throttle body just in front of the butterfly. If the hunting stops then it's quite likely that valve is shagged.
I've killed several cold idle valves. They don't like the coolant getting hot... I found that anything above three quarters on my guage starts to kill them.

yea i had to move mine to get the banjo off the fuel rail, that was another thing i was thinking it could be, its also Surging as well when trying to cruise at a slow steady speed.

i marked the TPS and put it back to where i had marked it, obviously not 100% accurate and not sure how sensitive those things are.

[Stealer Of Souls]

Sensitive, but not that sensitive. If you marked it and put it back much the same it should be okay. Unless it was borderline to begin with. I would first point the finger at the cold idle control valve.

[pc]

Mine fluctuates really badly when the O2 sensor is unlplugged... could be this?

[repowered]

I would first point the finger at the cold idle control valve.

is this the cold idle control valve?

that would only affect the cold idle though?, the hot idle is too high as well, the throttle is stopping on that screw that stops the butterfly bottoming out on the TB.

Sensitive, but not that sensitive. If you marked it and put it back much the same it should be okay. Unless it was borderline to begin with.

okay i'll double check its back on my marks, how easy is it to set correctly - ive read the FAQ and printed that PDF out on it but need bit more of a howto

[2LTR Rona]

is this the cold idle control valve?

Correct, the control valve is housed inside the unit the two water lines are hose clamped to, if you where to take that unit off you would be able to see that water passes through the valve & is opened when at X operating temp.

One of those lines is the "from" block and the other is the "return" to the block

[repowered]

ahh cool i thought i was that round thing. i'll check it out.

[Stealer Of Souls]

The cold idle valve is supposed to shut completely when hot.

There is a spring that tries to pull that valve open and some wax that pushes it closed. But if the wax inside of the valve has died then it doesn't shut the valve properly. The engine's vaccum pulls the valve closing it (idle drops) then the vaccum drops and the spring pulls the valve open again (idle rises again). And this pretty much continues on that sort of path...
(I'm pretty sure I've got that around the right way, it always confuses me when I think about it too long)

[repowered]

The cold idle valve is supposed to shut completely when hot.

There is a spring that tries to pull that valve open and some wax that pushes it closed. But if the wax inside of the valve has died then it doesn't shut the valve properly. The engine's vaccum pulls the valve closing it (idle drops) then the vaccum drops and the spring pulls the valve open again (idle rises again). And this pretty much continues on that sort of path...
(I'm pretty sure I've got that around the right way, it always confuses me when I think about it too long)

cheers, ill take the one off my spare motor and see how it works, i sopose you wont be able to see it fully open as when you take it off it may have closed again as you will have to drain some coolant i guess.

[Leon]

I've had a bouncing idle on 4AGE's with the O2 sensor unplugged, and also with a blown headgasket leading to cooling system bubbles.

[l1ttle_d3vil]

i sopose you wont be able to see it fully open as when you take it off it may have closed again as you will have to drain some coolant i guess.

thats when you block off the hole inside the throttle body, as mentioned above. if the valve is fully shut [once warm], when you cover this hole up with your finger it shouldn't effect the revs at all. im pretty sure thats the right way around...
ive actually got rid of my idle up valve all together, just got an alloy plate screwed in to block all the holes up. alot less water lines goin all over the place that way too! only problem is it idles a little bit low when dead cold sometimes, but nothing major.

and as for the surging at a steady speed - you meaning you can't "ease on" the gas, or hold it to keep your speed steady? that would probably be a dodgy TPS. i spent ages trying to set mine exactly right, and rechecked all the specs again and again and they were sweet but it kept surging. swapped it with another one, set it up once and it has been going mint ever since.
repowered - if you're coming to taupo on nov 18th come see me; ill show you how mines set up. mind give you some ideas for yours.