Idle speed problems

["checksix3" <checksix3@xxxx>]

Did you get this solved? Shouldn't be too difficult, its likely 
mechanical binding, misadjustment, or electronic. 

One at a time:

>>>>i adjusted the spring on the throttle one more notch. it's 
pretty tight now (i think mine was already adjusted forward). i also 
adjusted the throttle linkage. right now it is all set up so that if 
i have the pedal to the floor, the throttle hits the full throttle 
switch, and when i let the pedal all the way back down, it is pushing 
on the idle speed switch w/o any additional play on the switch.<<<

Be sure that when it hits the idle switch the throttle plates are 
completely closed. Adjust that *first*, then set the idle switch. 
When you are done, be asolutely sure there is no mechanical binding 
in the system.

>> when i have a screwdriver pushed down on the idle speed switch, 
my idle screw is adjusted so that i am running at about 800 rpm or 
so. STILL, when i put my foot on the gas and let the pedal back 
down, the idle doesn't kick down!!! it sits at about 1200 RPM. 
however if the car is at say a stop sign, i can hit the gas with my 
foot on the clutch and let it drop down fast, and THEN it will kick 
down. i can't find any mechanical reason why is should be like 
this. i would think the switch doesn't care if it is tripped hard or 
softly - it is still being tripped.<<<

It doesn't care if tripped hard or softly, its just a contact 
closure. After being sure the throttle plates are closed (using the 
other adjustment screw nearby), set the idle switch screw to depress 
the idle switch only enough to close it. You should still be able to 
reach in there and push it more after it clicks. You don't want it 
to "bottom" out, ony actuate. Bottoming it out will stress the 
actuator attachment point. (Air cleaner is off to do this.) From what 
you're saying, it appears your ISC systems is working and you have 
binding or other issues. 

>>>1. how far into the idle speed switch is too much? should the 
screw be pushing on the switch all of the way, medium, or just enough 
to take the tab off the switch?<<<

see above, just enough to close the switch.

>>>2. basically every adjustment you make throws something else 
off. how do i set up the linkage so that when the pedal is fully 
depressed i know that the throttle butterflies are wide open?<<<

Your problem is idle. We can worry about making full throttle and the 
WOT enrichment switch after you fix the idle. Forget about it at this 
point. (The WOT switch is not connected to the ISC system.)

>>>3. the shop manual says that the idle ECU recieves a ground when 
the butterflies are fully closed. if my butterflies are off, perhaps 
my ECU isn't recieving a ground all of the time unless i let the gas 
off quickly, maybe hitting the butterflies hard and making it all 
work? just a theory. how do i test it?<<< 4. how do i know if my 
idle speed motor is working? under which conditions should which 
things happen. i'm not proficient with a DVOM so if anyone has 
any ideas, they will have to tell me how to hook everything up.<<<<

The idle switch basically "wakes up" the idle ECU by powering it.
The ECU has no ground point other than the switch, so its dead until 
the switch is made. Can you use an ohm meter to measure the switch 
closing? You can also use a voltmeter and it would be easier if you 
knew how to do this. If not, here are two ways to test most of the 
ISC system:

1) when the car is warm and idling, disconncet the idle switch. The 
idle should increase. 2) With the car idling, grasp the throttle 
spool and increase throttle only enough to lift off the idle switch 
tab. Holding this position (about 1000-1200 RPM), use a screwedriver 
to depress the idle switch actuator tab back down. Idle should 
decrease. If either of these happens, its pretty much working.

>>>is there something else i'm missing? i'm inclined to believe my 
butterflies are part of the problem. i really need someone to guide 
me through complete adjustment of the throttle system.<<<

What you want is this: 1) throttle plates fuly closed. 2) Idle 
switch "made" just enough to close it. The throttle stop screw is on 
the plate, the idle switch screw is just depressing the switch tab 
enough to actuate it. 3) No mechanical binding. Look inside the 
throttle spool. The spring bends around the center pivot post. It 
must not touch the post, only curve around it. If it touches, unhook 
it and bend it so that is does not touch the center post. If the idle 
switch is made everytime you you release the throttle, you have no 
binding and this is not your problem.

To set it up from scratch: 

1)Loosen both lock nuts on the throttle stop screw and the idle speed 
switch screw and back the screws way off.

2) Disconnect the throttle linkage and allow the throttle plates to 
close. Maybe disconnect the accel cable also.

3) To be sure they are closed, gently push on the ball attached to 
the throttle plate linkage. You should see no more movement. If you 
want to know for sure, you'll have to remove the pipe and eyeball 
them.

4) Make sure the throttle spool is all the way back. Have some 
slight slack in the cable. Make sure everything is all the way back 
and nothing (throttle screw, idle screw, auto trans cable, 
accelerator cable, etc) is holding the throttle plates open. Be sure 
the entire thing is at "rest". Check for binding in the throttle 
plates *and* the cables, spool, etc. Now is a good time to check for 
binding because you have the linkage connecting the two seperated. If 
all is OK, sdjust throttle linkage to fit and install it.

5) Turn throttle stop screw in until it just contacts the stop 
plate. Watch it closely until it *just* starts to move the linkage. 
(starts to open the throttle plates) Lock it in this position.

6) Adjust the idle speed switch screw to just actuate the switch. 
(not touch it, but actuate it). Lock it in this position. Slightly 
open the trottle by grasping the spool. Make sure the idle switch 
clicks open. Release the spool and makes sure it clicks closed. Put 
an ohm meter on the switch (after disconnecting the wires if you 
wish, or at the ECU connector) to be sure it is opening and closing.

The throttle stop screw should contact the plate just after the idle 
switch closes (or almost at the same time) with the throttle plates 
closed. Bascially, the throttles and idle switch should be closed 
with their stop screws taking the "load" so they are not forced 
further closed by the linkage.

You likely have either binding or electrical problems. I'm betting 
binding. Look inside at the spool return spring, I've seen that cause 
binding before. 

Want to remove the idle speed function for testing purposes?
You need to "break open" the feedback closed loop and go to manual 
idle. (No need to do this if the ISC system test I mentioned above 
checks out.)

1) Either unplug the idle speed motor, one wire off the switch or 
unplug the idle speed module behind the drivers seat.
This will "fix" the ISC valve at whatever position it happens to be 
in. (Its a rotary valve, kinda like a stepping motor.)

2) Remove the idle speed valve and plug both hoses or leave it 
installed and pinch off or plugged the hose that leaves the idle 
speed valve and goes to the manifold. Either hose will do, the one 
towards the rear of the car is easier to get at. (Best to remove the 
motor and plug both of them, pinching hoses is for Neanderthals.)

3) Open the idle adjustment screw on the manifold a few turns and 
start the car. Make sure you're adjusting the idle speed and not the 
air balance screws. See your manual. Warm the car up and set the idle 
to about 800 to 1000 rpm. Doesn't matter, this is for testing.

You now control the idle using only this screw to let air into the 
manifold. You now have "open loop" idle control. Manipulate the 
throttle. If the idle consistantly recovers to *about* what you set 
it at, then the problem is in the idle speed system (motor, switch, 
ECU or wiring) If it *still* is not repeatable, check for binding or 
problems in the linkages or cable. (If you have an auto transmision, 
don't forget the govenor cable.) I suspect a throttle spool spring 
touching the center post as described above. If it is touching, 
correct that and put the spring back from the one notch you moved it.
Also lubricate the spool while you're in there.

Electrical problems could be as follows:

1) Bad ECU 
2) Bad wiring
3) Bad idle switch
4) Bad cold idle thermistor.

There is a thermistor that monitors the coolant temp. It results in a
fast idle when the engine is cold (below 59F, as I recall). Btw, I 
manipulate this circuit to idle up my car when the AC, headlights, or 
fans are on. I have an adjustable pot so I can select the high idle, 
it doesn't effect the cold idle setting.

This thermistor could be bad, but I doubt it. Other items to check are
CO adjustment (is the plug there?), idle and air balance screws (all 
three should be closed) and binding in the air balance plate or 
control plunger. With the car off, remove the air filter housing and 
gently push down on the plate and see if it returns to the same 
position. You will lose your fuel system resting pressure and flood 
the engine some (may be hard to start immediately thereafter) so 
don't do this too many times. (I doubt this is the problem however.) 
Does the idle hunt when cold? This common problem is most often 
caused by slight misadjustment of the CO setting.

You could have some weird problem, such as a funny tach signal. (Its 
the "process variable" in the ISC system, what you're actually trying 
to control) but I doubt it. At anyrate, its always best to open any 
feedback loop to troubleshoot it.

Some time spent with an ohm meter/voltmeter at the ECU connector will 
tell you if the sensors and wiring are OK. Let me know and I'll walk 
you through it. Opening the idle speed feedback loop will tell you 
alot, its difficult to troubleshoot closed loop systems as, if not 
set up correctly, they tend to oscillate as they chase the setpoint.

All this should reveal the source of the problem and you can go from 
there. After you get this figured out you can check the WOT 
enrichment and auto trans kickdown (if you have one) switch settings. 
Let me know and I'll offer more help if needed.

Good luck,

Gary