Idle Air Control Valve

[alain173]

Hey Folks,

I did some research on this board concerning my high idle at start-up (2K). All roads led to IAC. Well, I pulled it, cleaned it , and put it back. The car started up and idled about 1200 at first, then climbed to about 1800. I guess thats better than 2k, but i would like to lower it further. I hear my valves tick momentarily in the morning when it launches to 2k. After it warms up, my idle is fine, stable at 600. Any other ideas? Do I need to replace the IAC? Thank you.

 

[RavenTai]

o-ring trick

http://www.safari4x4.com.au/80scool/tech/fast_idle/fast_idle.html

 

[SR.GRINGO]

Check your TPS according to the fsm--mine was bad. Got a new one from Dan--she idles at about 6.25

 

[IdahoDoug]

So, any here on Mud that have done this and have permanent results fixing the high cold startup? I'm doing some major maintenance next week and may include this.

DougM

 

[alain173]

Thanks for the replies. I will try the o-ring method. I have hope that it will help. I will update this thread with the results. Has anyone tried this procedure with a favorable outcome? Thanks.

 

[othater]

Is the safari website down? I like to see how to due the O-ring fix. Does anyone else have the write up?

 

[RavenTai]

So, any here on Mud that have done this and have permanent results fixing the high cold startup? I'm doing some major maintenance next week and may include this.

DougM

not here, mine is only high for the few start ups after disconecting the battery, after that it learns,

I remember some posts where others have reported good sucess with this trick.

 

[TroutBear]

Looking forward to replies on this issue as we have about the same thing on our '94. I'm headed to pull up the files on the FSM and read up on the suggested page, but how much did a TPS run from Dan?

 

[alain173]

Guess what? I might have jumped the gun, because now and for the past couple of days, the car has fired up and idled at 1200rpms when cold! Then it settles down to 600rpms when warm. I guess it fixed itself after I cleaned out the IAC valve. I can't believe it. I'm as happy as a clam!

 

[Scamper]

So, any here on Mud that have done this and have permanent results fixing the high cold startup? I'm doing some major maintenance next week and may include this.

DougM

I kinda view the o-ring fix to be a workaround for a problem someone either can't diagnose or won't bother to. IMO, if the startup idle is high, there must be a reason leading to this--after all, the truck presumably ran fine when new... There have been quite a few discussions on the IAC, TPS, throttle cables, TB cleaning, etc., and I've always thought these high idles had to do with one or more of those being out of adjustment or failing, rather than anything else. JMHO.

 

[MoGas]

I kinda view the o-ring fix to be a workaround for a problem someone either can't diagnose or won't bother to. IMO, if the startup idle is high, there must be a reason leading to this--after all, the truck presumably ran fine when new... There have been quite a few discussions on the IAC, TPS, throttle cables, TB cleaning, etc., and I've always thought these high idles had to do with one or more of those being out of adjustment or failing, rather than anything else. JMHO.

I was using the oring trick for a while and it worked well for me. I have since removed the orings and am trying to properly diagnose the fast start idle issue.

The FSM recommends that you check the following in this order for
'Incorrect first idle". I am including what results I have had so far.

1) Accelerator linkage.

I have replaced my cable recently with no change in the idle issue. I have ruled out the possibility of the cables causing the high start speed by removing the cruise and throttle cables and allowing the truck to sit overnight then starting in the morning and still getting the fast speed.


2) ECT sensor circuit.

I did all the checks as prescribed in the manual including removing the ECT sensor and checking the resistance as the water temperature raises in the water pot. The ECT sensor and circuit checked good.

3) IAC valve. I am going to do these checks in the next day or so.


4) ECM

I will also be thoroughly inspecting the harness at the EGR valve and firewall protrusion.

I'll keep y'all posted.

Dave

 

[semlin]

what i can tell you is that if i remove and replace the throttle body, even without cleaning it or touching the tps/iac, it fixes the high idle then it gradually climbs back. i learned this replacing the egr valve a while back and then it did it again during the h/g.

imo this narrows it down to some kind of memory in the tps or iac that is lost when you disconnect them or else the cables. i have not tried just disconnecting the tps and iac.

incidentily, who knows what the dashpot does?

 

[treehugger]

oooooooooooooooooooooooooooooooooooooooboy

 

[RavenTai]

incidentily, who knows what the dashpot does?

It cushions/slows closing of the throttle plate, I am not sure if this is to give the IAC time to come on line and take over or just as simple as keeping the plate from slamming closed and wearing the stop and shaft as long as it is not jammed and preventing the closing of the throttle plate then it should not have any effect.


there si an adjustmet in the FSM

3. INSPECT AND ADJUST DASHPOT
(a) Allow the engine to warm up to normal operating temperature.
(b) Connect the LEXUS hand–held tester or OBD II scan tool.
(c) Check the idle speed.
Idle speed: 650 ± 50 rpm (N position)
(d) Open the throttle valve until the throttle lever separates
from the dashpot end.
(e) Release the throttle valve gradually, and check the dashpot
setting speed when the throttle lever touched the
dashpot end.
Dashpot setting speed: 2,200 ± 300 rpm
If not as specified, adjust using the following procedure:
Stop the engine.
Loosen the lock nut of the stopper bolt.
Using a 2.5 mm hexagon wrench, adjust the dashpot
setting speed by turning the stopper bolt.
Start the engine and check the dashpot setting
speed.
Retighten the lock nut.
(f) Maintain the engine at 3,500 rpm.
(g) Release the throttle valve, and check that the engine returns
to idle in a few seconds.
(h) Disconnect the LEXUS hand–held tester or OBD II scan
tool.

 

[semlin]

i assume dashpot setting speed is an obd2 readout? there is a procedure in the obd1 truck fsm too that I have never tried.

 

[RavenTai]

i assume dashpot setting speed is an obd2 readout? there is a procedure in the obd1 truck fsm too that I have never tried.

It does not specify, "connect Lexus hand held tester" is in just about every procedure weather it is needed or not,

I would assume that the tachometer could be used just fine though you might need an assistant to watch it wile you watch the dashpot.

 

[ARB777]

Bringing this back from the dead. What is the o ring trick?