95 Tacoma 3.4 High idle

My truck will not idle down. I have tried everything. A friend has a
salvage yard and I have swapped about everything: Entire throttle body
with sensors, Cam position sensor, Crank position sensor, TPS, IAC, ECU.
The only one i havent done is the O2. I have rechecked the timing belt
after I changed it and it is correct. It was fast before the change as
well. I have sprayed all over the intake and all hoses looking for vacuum
leaks and cant find any. I GIVE UP!! Somebody else try. Thanks.

RobertM wrote:[color=blue]
> My truck will not idle down. I have tried everything. A friend has a
> salvage yard and I have swapped about everything: Entire throttle
> body with sensors, Cam position sensor, Crank position sensor, TPS,
> IAC, ECU. The only one i havent done is the O2. I have rechecked the
> timing belt after I changed it and it is correct. It was fast before
> the change as well. I have sprayed all over the intake and all hoses
> looking for vacuum leaks and cant find any. I GIVE UP!! Somebody
> else try. Thanks.[/color]

You could have a bad or disconnected temperature sensor. This would make the
ECU think the engine is cold constantly and kick in the cold idle motor.
Have you verified the linkage isn't the problem by unhooking while idling.
Dirt and gunk under throttle pedal will somtimes cause it to stick.
HTH, davidj92

Yes, the throttle plate is closing and I have replaced the coolant temp
sensor. Forgot to mention that one but it was the first one to replace.
It runs around 1100. The a/c switch is off and the power steering idle up
is not it either because when you turn the wheel it will speed up some
more, the same with the a/c.

RobertM wrote:[color=blue]
> Yes, the throttle plate is closing and I have replaced the coolant
> temp sensor. Forgot to mention that one but it was the first one to
> replace. It runs around 1100. The a/c switch is off and the power
> steering idle up is not it either because when you turn the wheel it
> will speed up some more, the same with the a/c.[/color]

If throttle plate is closing completely then I would look at cold idle
system. I'm not sure which system Toyota uses, there may be something stuck
open keeping engine in high idle state. I'll have the time to look in
service manual tomorrow and post any additions.
HTH, davidj92

It is showing on a scan tool about 57% Idle air speed open which seems very
high to be warmed up. I have tried two different Idle valves but no
change. I removed the cover of one of the valves to get access to the
little knob that turns by the motor of the valve. You can turn the knob
and it will idle down to the point it will stop running which leads me to
believe I don't have a vacuum leak. Thanks for the help!

RobertM wrote:[color=blue]
> It is showing on a scan tool about 57% Idle air speed open which
> seems very high to be warmed up. I have tried two different Idle
> valves but no change. I removed the cover of one of the valves to
> get access to the little knob that turns by the motor of the valve.
> You can turn the knob and it will idle down to the point it will stop
> running which leads me to believe I don't have a vacuum leak. Thanks
> for the help![/color]

I agree, that seems high for a warm engine. The only vacuum leak I can think
of that could cause this is between TBI and idle valve.

It seems to me if there was a vacuum leak it would read lower than normal
and be trying to overcome the leak. Just my thought.

"RobertM" <robertmays@aol.com> wrote in message
news:23efccfa41a6e4aca14c9bd2e558a0dd@localhost.talkaboutautos.com...[color=blue]
> It seems to me if there was a vacuum leak it would read lower than normal
> and be trying to overcome the leak. Just my thought.
>[/color]

Unless there is an electrical control seeing a low vacuum then I would
agree. I just read a post in Camry ng about a sticking slide in a idle
control valve. His problem was a stumble and low idle speed but a sticking
slide could cause the opposite, high idle speed.
He cleaned with TB cleaner and problem recurred. He lubed with TriFlow
aerosol lube for bicycle chains (PB Blaster has a good chain lube as well)
that doesn't attract dirt and problem solved. I attached his message JIC it
might help you.

---------------------------------------------------------
IAC is the idle air control valve.
This discussion relates to a 1994, 4 cylinder Camry.
Seems operation of this valve is a recurring problem.
Best information I could find on the Internet was to spray emission
control safe carburetor cleaner in the small square orifice at the
front/ bottom of the throttle body to restore operation, or replace the
valve.
Problem manifests as stumbling low idle when first starting up in the
morning, that is, the automatic fast idle for the cold engine doesn't
engage. If you put it in gear like that, it dies.
For the first couple of years, the carburetor cleaner worked fairly
well. Remove one hose clamp, short burst of spray, turn the ignition
switch on and off a few times, to try to force the valve to move and
all would be well for another few months.
Then the "cure" started to fade and the problem would recur within a
few days.
So I ordered a new idle air control valve and throttle body gasket and
consulted the Factory Service Manual.
The procedure for throttle body removal included procedures for
adjustment of the TPS (throttle position sensor), instructions for
cleaning with solvent and compressed air, and procedure for calibrating
a vacuum diaphragm which controls the butterfly throttle plate.
One of the vacuum ports had been at least partially blocked - now
cleared, the .012" setting on the TPS was off, and adjusted per spec.,
and the idle speed at the vacuum diaphragm with the line removed after
reassembly required adjustment.
I did all of this.
Since the old IAC valve was going in the trash, I disassembled it for
examination. There is a bimetallic thermostatic coil on one end of the
shaft and a round permanent magnet on the other end. The cylindrical
part with the port that moves to progressively open or close had a
small groove worn in it as if there had been some contamination or
binding.
All was well for about six months until the rough idle at cold start
returned.
Finally, the idea presented that there is no lubrication for that
valve.
Have been using TriFlow aerosol for the electrically powered antenna
after seeing this specialty lubricant in a bicycle shop - for use on
chains and cables, to lubricate without attracting dirt.
[url]http://www.triflowlubricants.com/[/url]
So I sprayed a small amount of TriFlow into the IAC valve on the theory
that perhaps that bimetal thermostatic coil is supposed to rotate the
IAC valve when cold, and if it sticks slightly, the spring pressure may
be insufficient to move it. The permanent magnet on the other end must
be part of the computer controlled step motor that adjusts idle speed
continuously to maintain the target value.
Works great. Idle speed when cold is very "fluid", that is, rises just
for an instant then settles slightly and adjusts downward as the engine
warms, just as it should.
So perhaps this is the solution for what appears to be a design
weakness in an otherwise superbly engineered vehicle - a way to keep
that valve moving smoothly without gumming up or attracting dirt.
We shall see.