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Discussion Starter #1
My Solara idle is always too low (often barely 500-600 rpm) and therefore not only idles rough, but so low that lights and accessories either go dim or slow down until stepping on the gas pedal. I have tried raising it with the throttle cable ending, and I have also tried raising it with the allen screw inside the set nut. Initially it works, but it seems that somehow it re-adjusts itself electronically back to the same thing no matter how I adjust those adjustments. . . frustrating.

Frankly, I don't see the point of even having those mechanical adjustments exist there if there is something electronic which is ultimately in control. It surely seems to me that there must be a way of adjusting the idle in a lasting way.

Have paid a shop a few times to "clean the throttle body", but that never seems to solve this, the idle still stays too low, and I feel like a bit of a fool for handing over my money for nothing.

Thanks for your kind help
 

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Almost 1/2 Million Miles!
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This is caused by a dirty or stuck Idle Air Control Valve.

I am pretty sure the 2000 Solara has this which is an Electro-magnet control valve with small Coolant Hoses going to it plus a vacuum hose, I believe.

My 1992 Camry suffered with this and I had to clean it like this gentleman:

 

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I have a 95 2.2l so not exactly the same engine but I was trying to raise my rpms a bit to eliminate some of the engine vibration at idle. I tried a TB off of a 91 or 92 Celica that had an adjustable air bleed screw to change the rpms. I could successfully raise the rpms, but within a seconds or two the ECM knew the rpms were off and would override my input and correct the idle speed back to the factory specs as dictated by the computer.
W95c
 

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Discussion Starter #7
Thank you guys for the quick responses!

This is actually a very old problem which I have had with the car since I bought it more than ten years and many miles ago. Two times over the years, I have cleaned the IAC. No improvement there. I had already watched all the videos suggested by guapoman2000 before I posed my questions on here. I can certainly clean the IAC again, and don't mind doing so. The car has always run well despite the low idle. It never stalls. When it is cold, the car idles beautifully. Over all these years, no error codes had ever shown up, and no idiot lights had ever illuminated. I have replaced wires, plugs, EGR valve, etc., etc. with no improvement. It just idles TOO DAMN LOW, which makes the lights a bit dim and makes it seem to idle a bit rough. As I've said, I was able to raise the idle temporarily a couple times, but the evil presence inside the mind of the car always detects my tinkering, and lowers it back down within a day or two.

I'm thinking there must be a less-mechanical, (maybe electronic?) means of telling this thing to low-idle a bit higher. Does anybody know??

Many thanks in advance for your kind and knowledgeable input on this. . .
 

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Toyota Collector
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There is no way to change the idle speed unless you introduce a large vacuum leak and you don't want that. Also the supposedly adjustable idle screw on a 3S (or drilling out on a 5S) throttle body will not change the idle what that does is rotate the relative position of the TPS. That can make the idle go up but over time the ECU will relearn and adjust the idle down, unless you turn the screw to the point where the TPS never gets to the idle position so the ECU always thinks the throttle is partially open. If you do this the transmission won't shift properly.

If you really want to raise the idle then rig up a adjustable stop that physically opens the butterfly valve but I don't recommend this.
 

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Discussion Starter #9
Thanks, 71Corolla. From what you're saying, and from my own experience with this, it seems clear that Toyota never intended for an end-user or backyard mechanic to be able to adjust the idle.

That much having been said however, I'm thinking there must be a backdoor method for a Toyota insider to change computer parameters. Surely, performance tuners must have figured out work-arounds to the limits of the programming.

Furthermore, the car cannot have been doing this when it was brand-new, or there would have been floods of complaints. Something must have changed or deteriorated on this car, but I just don't know what that could be. Certainly, if this car were brand-new, the dealership would be able to replace something defective, or make some adjustment, which would cause the idle to be in the normal range.

I would obviously prefer to fix this issue without modifying computer parameters, but what the heck could have changed since the car was new, causing this too-low idle?? Why does the computer think this is ok?? Is the problem the computer itself? If so, then I'd have to either change the computer, or change those parameters; in which case, I'd surely opt to change the parameters if it could be easily done.

I hope I am not being annoying by pressing the question! Many thanks again. . . you've all been very kind and patient with me.
 

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AFAIK Toyota ECUs of this era cannot be hacked (within reason) maybe I'm wrong. Have you put a tach or scan tool on the engine (not simply using the cluster) to see what the idle actually is?
 

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Discussion Starter #11
AFAIK Toyota ECUs of this era cannot be hacked (within reason) maybe I'm wrong. Have you put a tach or scan tool on the engine (not simply using the cluster) to see what the idle actually is?
No, I have not. I don't know the precise, actual RPMs, but it is most definitely low. If I slightly press the gas pedal to where the RPMs read about 800 on the tach, then the headlights brighten to normal.
 

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Discussion Starter #13
Why not get another throttle body and IACV, clean them up and see if it fixes your problem.
I guess that's an option. . . probably expensive, but I guess I'll look into that for the heck of it. If I knew it was a solution, I'd be all in, but a used, unknown part that I can't return seems likely to be a poor gamble. Thanks again for indulging my questions. . .
 

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Dunno if you have Cali or federal emissions (if federal, the underhood emissions sticker will say "49 state emissions" only, not "50 state emissions" or "49 state and California"), but if you have federal I have a cleaned and tested federal TB assembled with cleaned and tested IAC, PM me if interested.
 

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There IS an adjustment. See, the IAC has a cold idle bimetal spring. When you remove the IAC, there is a plate on the gasket (engine) side just below the venturi. You'll note slotted holes to attach. Loosen and rotate. Unless it's broken, then it's remove and replace.

Cosmo
 

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Discussion Starter #16
Cosmofennema, you have my 100% attention: Sorry to be obtuse, but I just don't quite understand. Can you restate and elaborate a bit? MANY THANKS!!
 

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Discussion Starter #17
Also, please know that my cold idle is beautiful. The warmed-up idle is what is too low.
 

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The IAC could still be to blame. For to see this bimetal, you MUST remove the throttle body. Once removed, look at the engine side, and just below the venturi is the plate hiding the bimetal. There is NO WAY to adjust this on the car, unless you're a rose-jointed monkey, AND the screws will cooperate, neither of which apply, here.
FWIW, I just soak the IAC and throttle body (disaasembled) in a gallon tin of carb cleaner. I also replace all screws with allen head cap screws. Bloody phillips head just don't age well.
 

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Discussion Starter #19
Okay, so if I understand you correctly: you're saying that the adjustment is on the throttle body itself. There is some kind of a plate which has slotted screw holes. I would need to loosen those screws and rotate the plate to adjust the idle. Is that right?

1. Does that adjust the warmed-up idle, or does that adjust the cold idle?
2. Which way do I rotate the plate in order to increase the warmed-up idle?
3. Will the engine computer override it, and lower it down again, like it does with the other idle adjustments I made? Why not?
 
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