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Discussion Starter #21
IACV was used from someone on this board. According to the repair manual, the diagnostic procedure for it is to remove it but leave the electrical plugged in, and what rotate back and forth as you turn the ignition key on and off.

Regarding holding down the gas pedal, it does nothing until I step hard enough that RPM's will hold at the top RPM "bounce point of the up/down/up/down bounce, meaning, if my idle is bouncing from 1000 up to 2000, I have to step on the gas hard enough to at least get it to 2000 before it will actually do something, hold steady and quit bouncing. There is no change in RPM's or the bounce if I push the pedal too lightly.
 

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Electromagnetic Wave :-h
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I've only had this happen to me a few times, early on in ownership, and then only not long after an ECU reset. The only way I could get it to stop was to shut down and restart. That seemed to clear it. Somehow the ECU can get into this funk where it ramps the IACV through its full range. Normally, it makes slow changes to the idle and saves the setting in the ECU. It may be related to checking before issuing an IACV range CEL? In any event, in closed loop, the ECU strives to set the idle at it's pre-determined RPM and meet it's target AFR. Just about any sensor (possibly intermittent) in closed loop could throw this off (especially a flaky TPS). A manifold leak, unless it is intermittent, would normally just be adjusted for by closing the IACV a bit more. Eventually, you would likely get a Too Lean CEL or an IACV range CEL. An intermittent exhaust leak would wreak havoc w/the AFR, though. Best advice is to look at it w/a live scantool when it is happening and see what the sensors are saying.

If you are going to check the throttle stop, here's the procedure:
 

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try disconnecting the purge VSV and see if it goes away.

Has anyone messed with the set screw on your throttle plate?
 

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Discussion Starter #24
I haven't messed with the set screw, but that's not to say previous owners didn't mess with it. It will be one of the things I will check today because even when it's warm outside (above 60F), the idle will still sit at around 1500 which is way too high. It won't bounce when it's that warm out, but it will idle too high. Regardless of what I do today, I am going to get a new MAF ordered. Speaking of temperature, it has now warmed up to a balmy -3F (and I'm not motivated to go outside!).
 

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if you have to put it above 2k for it to even out, its not the IAC... that would only be on the low point of the bounce trying to hold that speed.
 

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I haven't messed with the set screw, but that's not to say previous owners didn't mess with it. It will be one of the things I will check today because even when it's warm outside (above 60F), the idle will still sit at around 1500 which is way too high. It won't bounce when it's that warm out, but it will idle too high. Regardless of what I do today, I am going to get a new MAF ordered. Speaking of temperature, it has now warmed up to a balmy -3F (and I'm not motivated to go outside!).
If they have the throttle held open because they screwed with the set screw it does exactly that.
 

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im thinking tat if u gonna keep replacing stuff for nothing i think u should just take it to the toyota dealer shop and let them figure it out so u wont' be wasting stuff u dont need?
 

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Discussion Starter #30
im thinking tat if u gonna keep replacing stuff for nothing i think u should just take it to the toyota dealer shop and let them figure it out so u wont' be wasting stuff u dont need?
While I generally agree with your statement, I wanted to at least get a new cat installed because it was the right thing to do and certainly couldn't be helping anything (especially my fuel economy), and the MAF is a fairly common failure point on these cars and isn't that expensive to replace. And even though my car isn't exibiting more typical MAF failure-related symptoms such as stalling, hesitation, or low idle, I do question it at least partially because one of the resistors has a funny crust on it that won't come off.

But after replacing these two things, I am not going to buy anything else until I do some additional digging.

While we did get up to a heat stroke inducing 8F today, I did not get the motivation to go outside. Hopefully tomorrow will bring warmer temps....

While I haven't looked at the throttle stop screw, it is starting to make moreand more sense. Hopefully it will be the cause, becuase it is a simple fix. It might also explain why I get the sensation that I can't ever lightly feather the gas pedal. As soon as I step on the gas pedal, such as when in neutral and parked, the engine wants to either do nothing or start revving pretty darn good (3500+). The idle doesn't start out around 800 where it should be, so I can't feather it up to 1000 if that makes sense.
 

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Discussion Starter #31
Solved, finally! The fix? 15 seconds and I was done. It took longer to undo the hood pins, pop the hood release latch, and pop the hood up. The throttle cable was way too tight at the throttle body.

A month ago when I installed the new used IACV valve, I checked the butterfly operation and it seemed just fine. It could close all the way no problem. But I realized today, I checked this while the TB was NOT in the car (meaning throttle cable was not hooked up). So sure enough today when I popped the hood, I bounced my finger lightly off the throttle cable and noticed it was way too tight. Then I looked at the set screw and the stop bracket was a good 1/8" away! But, I knew the set screw must be ok because of what I found a month ago. So, I loosened up the two 14mm nuts holding the cable on to the throttle body, loosened it several turns (about 1/4" worth on the threaded shaft) and I was good to go!

Within 30 seconds of starting the car, I knew the problem was fixed. Normally, the car (when completely cold) would idle at the cold high idle for about 30 seconds to 60 seconds and idle would try to start to drop (normally), but by the time it got to about 1900RPM, the idle would start bouncing 30-60 seconds after starting the engine. Two minutes into starting the engine after adjusting the cable, the RPM's were already down to 1500 and it has never done that. I let it warm up for a few more minutes, took it for a quick drive, and by the time I got back, idle was down to 1100 and it wasn't even fully warm yet. The temp gauge was only up about 2 positions.

Fixed! Thanks for everyone's help, and a gold star to everyone that mentioned checking the throttle cable/set screw! That should be STEP ONE of anyone's diagnostics when they have idle problems. It literally takes seconds to see if the throttle cable is too tight (e.g. no slack) or see if the throttle stop bracket is even touching the set screw.

I bought a new MAF but haven't installed it yet. I'm going to see what happens after a few days of "normal." The new MAF does not have the "tan crust" on one of the resistors I mentioned in previous posts. So, the crust still bugs me (and it won't clean off).
 

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Solved, finally! The fix? 15 seconds and I was done. It took longer to undo the hood pins, pop the hood release latch, and pop the hood up. The throttle cable was way too tight at the throttle body.

A month ago when I installed the new used IACV valve, I checked the butterfly operation and it seemed just fine. It could close all the way no problem. But I realized today, I checked this while the TB was NOT in the car (meaning throttle cable was not hooked up). So sure enough today when I popped the hood, I bounced my finger lightly off the throttle cable and noticed it was way too tight. Then I looked at the set screw and the stop bracket was a good 1/8" away! But, I knew the set screw must be ok because of what I found a month ago. So, I loosened up the two 14mm nuts holding the cable on to the throttle body, loosened it several turns (about 1/4" worth on the threaded shaft) and I was good to go!

Within 30 seconds of starting the car, I knew the problem was fixed. Normally, the car (when completely cold) would idle at the cold high idle for about 30 seconds to 60 seconds and idle would try to start to drop (normally), but by the time it got to about 1900RPM, the idle would start bouncing 30-60 seconds after starting the engine. Two minutes into starting the engine after adjusting the cable, the RPM's were already down to 1500 and it has never done that. I let it warm up for a few more minutes, took it for a quick drive, and by the time I got back, idle was down to 1100 and it wasn't even fully warm yet. The temp gauge was only up about 2 positions.

Fixed! Thanks for everyone's help, and a gold star to everyone that mentioned checking the throttle cable/set screw! That should be STEP ONE of anyone's diagnostics when they have idle problems. It literally takes seconds to see if the throttle cable is too tight (e.g. no slack) or see if the throttle stop bracket is even touching the set screw.

I bought a new MAF but haven't installed it yet. I'm going to see what happens after a few days of "normal." The new MAF does not have the "tan crust" on one of the resistors I mentioned in previous posts. So, the crust still bugs me (and it won't clean off).
i'm glad that you got it fixed. I was just signing in here to tell you that I would send you my last IACV to test with but it looks like you figured it out.

I usually see a 850-900 rpm idle in summer/spring and this time of year it holds steady about 1k. Almost always 1500 on first start of the day.

Just so you know for future info Toyota will usually do a $250 diagnosis on your vehicle. This is what I had done after I had replaced my ecu and my car wouldn't start. They told me what was wrong and left the option up to me to fix it or have them fix it. So if you cant figure out and you just keep buying parts, tow the damn car over to them for two hours of diagnosis.

Putting that MAF on might help you fix your gas mileage and a/f readings IF the corrosion was leading to any high idle.
 

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do you have pics of where the nuts holding the cable is?


tks


Solved, finally! The fix? 15 seconds and I was done. It took longer to undo the hood pins, pop the hood release latch, and pop the hood up. The throttle cable was way too tight at the throttle body.

A month ago when I installed the new used IACV valve, I checked the butterfly operation and it seemed just fine. It could close all the way no problem. But I realized today, I checked this while the TB was NOT in the car (meaning throttle cable was not hooked up). So sure enough today when I popped the hood, I bounced my finger lightly off the throttle cable and noticed it was way too tight. Then I looked at the set screw and the stop bracket was a good 1/8" away! But, I knew the set screw must be ok because of what I found a month ago. So, I loosened up the two 14mm nuts holding the cable on to the throttle body, loosened it several turns (about 1/4" worth on the threaded shaft) and I was good to go!

Within 30 seconds of starting the car, I knew the problem was fixed. Normally, the car (when completely cold) would idle at the cold high idle for about 30 seconds to 60 seconds and idle would try to start to drop (normally), but by the time it got to about 1900RPM, the idle would start bouncing 30-60 seconds after starting the engine. Two minutes into starting the engine after adjusting the cable, the RPM's were already down to 1500 and it has never done that. I let it warm up for a few more minutes, took it for a quick drive, and by the time I got back, idle was down to 1100 and it wasn't even fully warm yet. The temp gauge was only up about 2 positions.

Fixed! Thanks for everyone's help, and a gold star to everyone that mentioned checking the throttle cable/set screw! That should be STEP ONE of anyone's diagnostics when they have idle problems. It literally takes seconds to see if the throttle cable is too tight (e.g. no slack) or see if the throttle stop bracket is even touching the set screw.

I bought a new MAF but haven't installed it yet. I'm going to see what happens after a few days of "normal." The new MAF does not have the "tan crust" on one of the resistors I mentioned in previous posts. So, the crust still bugs me (and it won't clean off).
 

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do you have pics of where the nuts holding the cable is?


tks
:confused: they are at the end of the cable where it meets the throttle body. The bracket is attached to your manifold.
 

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Discussion Starter #35
No I don't, but it's right at the throttle body on the front of the engine. The cable in question (there are 2 throttle cables on my 2000 GT-S) runs from a black box just behind the passenger headlight, up in front of the engine via black sheath, and to the throttle body. The throttle body is the first piece of "engine" after the air filter box and plastic intake tubing (though you may have an aftermarket intake?).

There are two 14mm nuts at the transition of the black cable sheathing to bare cable at the throttle body. This is what I adjusted.
 

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There's a writeup in the installs section i believe.. it's titled how to adjust your throttle cable. or something along those lines. it says where everything is located, including those nuts.
 

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To Mnwolftrack

hey bud i didnt read through ALL the posts back and fourth so you may have figured it out by now, but I have an integra with same problem, well it has had the rythmic idle from 2k down to 1500 back to 2k over and over twice now and both times it was due to a leak in an air hose ( vac. leak ) im almost positive that will be the main problem, or it may be due to the throttle cable, try checking tension shouldnt be tto hard on your celica, a matter of loosening a nut or two to relieve tension or tighten. both times my car did it though, did a vaccum test and found a leak both times replaced hoses and boom stopped the idle bounce.
 

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hey bud i didnt read through ALL the posts back and fourth so you have figured it out by now, but I have an integra with same problem, well it has had the rythmic idle from 2k down to 1500 back to 2k over and over twice now and both times it was due to a leak in an air hose ( vac. leak ) im almost positive that will be the main problem. both times my car did it. did a vaccum test and found a leak both times replaced hoses and boom stopped the idle problem.
D and B series honda motors are cursed with a vaccum line on the backside of the block that can easily be knocked loose by your arm if you change your oil filter from the topside. It will cause the same behavior you are talking about adamjd26d
 

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Discussion Starter #39
hey bud i didnt read through ALL the posts back and fourth so you may have figured it out by now, but I have an integra with same problem, well it has had the rythmic idle from 2k down to 1500 back to 2k over and over twice now and both times it was due to a leak in an air hose ( vac. leak ) im almost positive that will be the main problem, or it may be due to the throttle cable, try checking tension shouldnt be tto hard on your celica, a matter of loosening a nut or two to relieve tension or tighten. both times my car did it though, did a vaccum test and found a leak both times replaced hoses and boom stopped the idle bounce.
This was solved almost a month ago, as mentioned a few posts up. The previous owner thought that a good way to manipulate your idle speed (on a vehicle where you cannot actually control idle speed) was to tighten the throttle cable until your "idle" is at the speed you want. He even posted about it in this forum!
 

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My 2000 gts does the same but just the first time started in the day.
Replaced intake gasket, throttle body clean twice, new gaskets, new o2 sensors, new idle control, maf, throttle pos, temp sensors, no vacuum leaks i can find. I have now given up! Car is a race car only and is fine on track. Sometimes the answer is “sod it”
 
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