Yet another 4AGE idle problem

[ChaosAD]

My 4age got the common problem of a fluctuating idle.

Tried turning down the idle screw but it still idles too high. I tracked the problem down to the cold idle valve under the throttle body.
When I put my finger over the hole where the valve sucks its air in the engine dies.
Should air be going throught this valve when the engine is hot?

[jondee86]

AUXILARY AIR VALVE.. The book says....
Inspect Air Valve Operation (w/o Air Flow Meter = with MAP Sensor)
(a) Remove the air cleaner hose.
(b) Check the engine rpm by closing the air port on the throttle body
(= put your finger over the sucking hole )

At low temp (coolant temp below 80 deg C.... the engine rpm should drop.

After warmup.... check that the engine rpm does not drop more than 100 rpm.

If operation is not as specified, replace the air valve.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Sooooooo.... as I understand it, this says that there will be a lot more air
running through the valve when the engine is cold. Going by what you
have described the air valve must be stuck open.

You can confirm this by seeing if you can set the idle with the idle speed
adjustment screw (with the engine hot) while you have the air port
blocked off.

Cheers...... jondee86

[ChaosAD]

Its definately the valve as it is letting in enough ai for the engine to idle at 1500rpm with the idle screw fully closed.

I have replaced the whole T/b (including idle air valve) with another one but that one could have been buggered too.

Or could it be a problem of not enough water getting to the valve? How would I check this? The pipes are warm so it should be getting water, right?

[ee904age]

It could be seized open like mine was. Pull it of and try to lever it unstuck with a screwdriver and give it some CRC.

That worked on mine as a new one from toyota was like $500

[jondee86]

You could check to see if both the in and out water hoses get hot... they
should be about the same temp as the radiator hoses once the engine is
fully warmed up (maybe try disconnecting one hose briefly to make sure
there is a good flow).

The valve appears to have a spring loaded metal cone connected to a
thermostat. As the thermostat heats up it pushes the valve closed. As
suggested, it could be worth looking inside to see if it is jammed open.

But, since I believe this valve is designed to aid starting in seriously cold
countries (sub-zero conditions), the car should run OK without it. Find a
small rubber bung to stop up the air port. Set your idle, and try it out for
a while. Post the results here

Cheers...... jondee86

[redline racer]

I had the same prob on my fxgt, tried to fix it many ways ie. block the bypass hole in front of the butterfly and drill a smaller hole in it, block the hole completly, clean out the valve etc, with no result. One of these ways may work in your situation and might be worth a try but i just ended up buying a new unit from toyota for about $200 and it is perfect now.

[liftback]

Pretty much all of these engines have this problem - mine did. Its an age related deteriation of the valve usually - and so the only thing you can really do is replace it. I didnt bother because i was qouted about $300 for it.

Check you TPS too as mine was faulty and was part of the reason why it was idling high (once that was fixed i would only occasioanlly have a high idle problem due to the valve)

[levin_it_large]

how much a new TPS cost? think i've got the same problem

[liftback]

No idea - i got one second hand for $20 off a toyspeeder. Dunno what they're worth new.

[ee904age]

levin it large: id suggest calibrating your tps 1st, if you buy a new one and bolt it on there is a 99% chance it will still give the same problem.

There was a post a while back from HRT on what the specs should be. You will need feeler guages and a multimeter.