High idle, or not?

[BrianZ]

I have this 85 GTS with working AC and everything.

It idles at aroung 1300 - 1400 when the AC is off and foot off break, 1500ish when you keep your foot on the break with AC off. and 900 - 1000ish when the AC is on.

I have hear these car idle a little high normally, but not sure.

So is it normal for my car to idle at such rpms?

If not, what should I do?

Somebody recomended me to replace the idle air control valve, I have called some major part store and they don't have them avaliable, and I have no idea where can I get one.

Please help.
Thanks!!

[jondee86]

Normal idle with A/C OFF, lights, brake, heater etc all OFF, should
be around 850-900rpm. There are three items that affect idle...

- Thermostatic Auxiliary Air Valve (raises idle on cold starts)
- Electric idle-up valve (raises idle 100rpm for electrical loads)
- Electric A/C idle-up valve (raises idle when A/C turns ON)

I suggest you start with the AAV as outlined here...
http://club4ag.com/forums/viewtopic.php?f=9&t=12013

Cheers... jondee86

[BrianZ]

Normal idle with A/C OFF, lights, brake, heater etc all OFF, should
be around 850-900rpm. There are three items that affect idle...

- Thermostatic Auxiliary Air Valve (raises idle on cold starts)
- Electric idle-up valve (raises idle 100rpm for electrical loads)
- Electric A/C idle-up valve (raises idle when A/C turns ON)

I suggest you start with the AAV as outlined here...
http://club4ag.com/forums/viewtopic.php?f=9&t=12013

Cheers... jondee86

I will try to clean the AAV this weekend.
But one thing I have noticed is that if I turn the idle speed adjusting screw all the way to the lowest point and with ac, lights and break off, it idle right at 900ish. But once I turn on the AC it drops to 500 and the whole car starts rattleing.
I know there is a spring kinda thing that suppose to adjust the ilde rpm when the AC is on, I have tried to adjust it as well, but it acts like the same as the idle speed adjusting screw (increase or decrease the idle when ac's off).

Any thoughts? Or how do I suppose to adjust that thing?

[jondee86]

OK... lets try a few diagnostic tests before we start ripping stuff apart

1. The AAV - cold engine, A/C and all accessories off. Start the engine
and observe. If the idle immediatly goes up to 2200rpm or somewhere
close, and then slowly comes down to 900rpm or close as the engine
warms up, the AAV is working.

2. The electrical load Idle-Up valve - A/C and all accessories off. Get
the engine warmed up and idling at 900-1000rpm. Turn on the lights or
step on the brake. Does the idle go up by around 100-200rpm and come
back down if you take your foot off the brake or switch off the lights ?
If so, the electrical idle-up valve is working.

3. The A/C Idle-up valve - A/C and all accessories off and engine warmed
up and idling at 900-1000rpm. Switch the A/C on... the engine speed should
stay around 1000rpm or perhaps raise by 100-200rpm. If it does, the A/C
idle-up valve is working.

Now in your case, you have said that the idle speed drops to 500rpm when
you turn the A/C on. Clearly your A/C idle-up valve IS NOT working.



This is a simple 12V solenoid valve that switches ON every time the A/C
compressor clutch engages. When the A/C is ON you should be able to
adjust the idle speed by turning the screw with the spring. So you need
to check if the valve is getting 12V, and if it is, is the valve working. The
valve could be borked, or you could have a wire broken/unplugged. Check
that the adjusting screw has not been wound closed.

If the valve is working, you adjust the screw until when the A/C clutch
engages, the idle stays the same or rises slightly. If the valve is borked,
you can probably grab one off any 80's Toyota in the junkyard.

Cheers... jondee86

[Deuce Cam]

Here's the process for checking idle speed in the service manual:

1. Engine is good and warm (e.g. after a 10-15 minute drive).
2. All accessories off
3. Foot off the brake
4. Race engine to 2500 rpm for a few seconds in neutral
5. Observe idle speed

[allencr]

Does the idle speed change when it warms up(1-3 minutes to drop down 500-1500rpm) or does it not???????
Checked REAL WELL for air leaks?
TB throttle plate's stop bolt& lock nut set for ZERO clearance, and slack in the cable letting throttle close completely?

[BrianZ]

Does the idle speed change when it warms up(1-3 minutes to drop down 500-1500rpm) or does it not???????
Checked REAL WELL for air leaks?
TB throttle plate's stop bolt& lock nut set for ZERO clearance, and slack in the cable letting throttle close completely?

It does drop back to 1300ish when warms up, cold start jump to 1900ish.

[allencr]

Does the idle speed change when it warms up(1-3 minutes to drop down 500-1500rpm) or does it not???????
Checked REAL WELL for air leaks?
TB throttle plate's stop bolt& lock nut set for ZERO clearance, and slack in the cable letting throttle close completely?

It does drop back to 1300ish when warms up, cold start jump to 1900ish.

OIK, great, now we all know or can assume that the coolant heated cold start AAV thingy on the TB is doing something, like working OK, and we can look somewhere else for making the idle what it should be & fix it. Then we'll look at the other air bypass electric thingy that bumps the idle up for the AC & other times when it isn't needed but you're stuck with like fan & brake lights & headlights.

[BrianZ]

Does the idle speed change when it warms up(1-3 minutes to drop down 500-1500rpm) or does it not???????
Checked REAL WELL for air leaks?
TB throttle plate's stop bolt& lock nut set for ZERO clearance, and slack in the cable letting throttle close completely?

It does drop back to 1300ish when warms up, cold start jump to 1900ish.

OIK, great, now we all know or can assume that the coolant heated cold start AAV thingy on the TB is doing something, like working OK, and we can look somewhere else for making the idle what it should be & fix it. Then we'll look at the other air bypass electric thingy that bumps the idle up for the AC & other times when it isn't needed but you're stuck with like fan & brake lights & headlights.

one thing i have noticed is that the rpm drops when i switch the ac on, so as jondee86 said above, my ac idle-up valve might not be working at the moment, i am in the process of getting a wroking, and i will be cheking see if i am getting 12v when the ac is on.

BUT!!! one thing I have noticed as well, if I adjust the spring on the idle-up valve WHILE the AC is off, it will raise or decrease the idle, just act act like the idle adjusting screw on the throttle body, BUT if i adjust it while the ac is on, I did not see a whole lot of difference in term of the idle...

[jondee86]

BUT!!! one thing I have noticed as well, if I adjust the spring on the idle-up
valve WHILE the AC is off, it will raise or decrease the idle, just act act like
the idle adjusting screw on the throttle body, BUT if i adjust it while the ac
is on, I did not see a whole lot of difference in term of the idle...

When the A/C is OFF the idle-up valve should be closed (no air passing) and
adjusting the screw should make no change to the engine speed. It should
only change the engine speed when the A/C is ON and the valve is open to
pass air.

So what can be deduced from this information ? That the idle-up valve has
failed in the open position, and that the adjusting screw has been turned
down to bring the engine idle speed down when the A/C is OFF. Thus, when
the A/C is turned ON and the valve does nothing, your idle speed will drop.

I have no idea if it is possible for the valve to fail/get stuck in the open
position. One check you can do is make sure the A/C is switched ON and
then wind the adjusting screw all the way out... see if you can bring the idle
up to around 1000rpm. Or if you like, use the screw to bring your warm idle
(A/C OFF) up to 1600rpm, and then turn the A/C ON and see if it drops to
around 1000rpm.

Cheers... jondee86

[BrianZ]

All right, new development.
I just went to check, and found out that when the AC is on, the AC light doesn't stay on. It will swich on for a few second, and then off for a few second, and then on... When the light is ON, it idles right above 1000rpm, but when the light is OFF, it drops to 600-700ish... then ON, 1000RPM, OFF 600RPM.. so on and so for...
Any thoughts?

[jondee86]

That's a trouble light for the A/C system. It comes on to tell you
that the A/C compressor has been turned off because of some fault.
Could be low gas or high pressure or low rpm <== most likely

This behaviour does not conflict with the deduction outlined in my
previous post. A/C turns on and pulls the rpm low. Control cuts the
A/C to prevent stalling, and the idle goes back up. A/C turns on and
pulls the rpm low.... repeat until bored.

Diagnosis still stands.... A/C idle-up valve not working.

Cheers... jondee86

[BrianZ]

Ok, so I bought a AC idle from a forum member and got it today.
Swapped it in, and it does the same thing. Still of I adjust the screw it will bring the idle rpm up or bring it down when the AC is OFF.
But I spotted a plug that was not plug into anything (the yellow one in the pic), so out of no where I plugged the green one and plugged the yellow one into the AC idle up. It basically did nothing, that's not the point. BUT I have noticed that when the green one is unplugged, the idle did not increase when I stepped on the break or turn on the light. But once I plugged the green one back in, everything is normal.



I don't know if I am wrong or not but isn't the increase of idle when heavy load kicks in is controlled by another unit other than the AC idle up?

[jondee86]

Does the A/C idle-up valve get 12V when the A/C compressor switches on ?

Cheers... jondee86