fast idle problems
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Lexus Champion
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From: Vancouver BC Canada
I just went and looked at one I have and it looks like you could take the black part off and then you can turn the little round fitting on the end of the actual valve and change the RPM. It doesn't seem like it would leak vacuum. You would be doing exactly what the electro magnet does. The valve is a cylinder and doesn't really turn very far at all.
You do realize that the black part that houses the electromagnet has an adjustment to it, right? There are slotted holes where the 2 screws that hold it on go. IF it needs replacing, what you get in the new part is the black part AND the part it screws to (the small pot metal part that actually has the cylindrical valve in it) The "motor" is actually an electromagnet that moves either way depending on which way juice is fed to it.
The throttle body does not have to be replaced. I have one caution. I have factory CD and the figures seem to be wrong. I have read once before on the forums that Lexus admitted they are wrong. The manual shows a resistance of 17.0-24.5 Ohms cold and 21.5-28.5 Ohms hot. The ohms are read from the center contact in the black part to either side (open or closed) The one I have measured something like 2 Ohms on one side and 59 Ohms on the other side and yet once I cleaned it thouroghly , it worked perfect.
he used throttle body cleaner and then blew it out with compressed air... no change.
If you take the IACV off (by draining some of the coolant and removing the screws on the bottom), you can leave it connected to the plug and test it's operation because then you can see what the valve does perfectly. I assume your mechanic has the manual, if not, let me know and I'll give you the procedure.
Thread Starter
Lexus Champion
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From: Vancouver BC Canada
i need to add something... when coasting on a slight to moderate downhill grade (ie. in gear, but not on the gas, holding a constant speed), the engine starts to surge, as in the car accelerates/decelerates on it's own with the rpms jumping roughly 500rpm in either direction. stepping on the brake makes it stop. this surging also happened only once at a stoplight. i was lightly on the brakes when the first surge happened and the car pushed over the stop line before i could catch it 
Lexus Champion
Joined: Feb 2008
Posts: 1,709
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From: Ca.
i need to add something... when coasting on a slight to moderate downhill grade (ie. in gear, but not on the gas, holding a constant speed), the engine starts to surge, as in the car accelerates/decelerates on it's own with the rpms jumping roughly 500rpm in either direction. stepping on the brake makes it stop. this surging also happened only once at a stoplight. i was lightly on the brakes when the first surge happened and the car pushed over the stop line before i could catch it
Thread Starter
Lexus Champion
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From: Vancouver BC Canada
the mechanic says he wants to replace the IACV. he called the local lexus dealership and they quoted over $600 for the part(s)???
does anyone know where i can order the part(s) cheaper and will ship to canada asap? i also need help with part numbers?
does anyone know where i can order the part(s) cheaper and will ship to canada asap? i also need help with part numbers?
Last edited by Benjamin T; Nov 12, 2009 at 11:19 PM.
Lexus Champion
Joined: Feb 2008
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From: Ca.
You have to buy the rubber gasket separate (same with everywhere), but when I replaced the one on my DIL's RX, I used the old one which was in perfect shape and have had no leaks or problems at all in 3 1/2 years.
Lexus Champion
Joined: Nov 2005
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From: OH
Carson sells it for $206.23 and ships worldwide.
http://www.trademotion.com/partlocat...&siteid=214915
http://www.trademotion.com/partlocat...&siteid=214915
CL Community Team
Joined: Apr 2001
Posts: 16,557
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From: Austin, TX
IACV is where the rubber meets the road for idle control, but the problem can originate some-where else.
Also it can be as simple as replacing the diamond marked gasket [specially if the idle problem started with messing with IACV. Can you you also give us history ... was the idle ever good? What happened before it went bad.
To check for vacuum leaks, you can try spraying carb cleaner around vacuum lines. [even around the diamond marked gasket]. If the idle shoots up, look for cracks.
If every thing else fails and you can not figure out what is going wrong, you get into the mode of start replacing things one by one and then changing the IACV would be the first logical choice [Your mechanic may be at this point].
Salim
Also it can be as simple as replacing the diamond marked gasket [specially if the idle problem started with messing with IACV. Can you you also give us history ... was the idle ever good? What happened before it went bad.
To check for vacuum leaks, you can try spraying carb cleaner around vacuum lines. [even around the diamond marked gasket]. If the idle shoots up, look for cracks.
If every thing else fails and you can not figure out what is going wrong, you get into the mode of start replacing things one by one and then changing the IACV would be the first logical choice [Your mechanic may be at this point].
Salim
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Thread Starter
Lexus Champion
iTrader: (2)
Joined: Jun 2005
Posts: 2,174
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From: Vancouver BC Canada
Carson sells it for $206.23 and ships worldwide.
http://www.trademotion.com/partlocat...&siteid=214915
http://www.trademotion.com/partlocat...&siteid=214915
unfortunately it costs $60 to ship to me standard ground (at least 5-7 business days)... $180 if i want to overnight it. argh.
Last edited by Benjamin T; Nov 15, 2009 at 07:58 AM.
Thread Starter
Lexus Champion
iTrader: (2)
Joined: Jun 2005
Posts: 2,174
Likes: 0
From: Vancouver BC Canada
IACV is where the rubber meets the road for idle control, but the problem can originate some-where else.
Also it can be as simple as replacing the diamond marked gasket [specially if the idle problem started with messing with IACV. Can you you also give us history ... was the idle ever good? What happened before it went bad.
To check for vacuum leaks, you can try spraying carb cleaner around vacuum lines. [even around the diamond marked gasket]. If the idle shoots up, look for cracks.
If every thing else fails and you can not figure out what is going wrong, you get into the mode of start replacing things one by one and then changing the IACV would be the first logical choice [Your mechanic may be at this point].
Salim
Also it can be as simple as replacing the diamond marked gasket [specially if the idle problem started with messing with IACV. Can you you also give us history ... was the idle ever good? What happened before it went bad.
To check for vacuum leaks, you can try spraying carb cleaner around vacuum lines. [even around the diamond marked gasket]. If the idle shoots up, look for cracks.
If every thing else fails and you can not figure out what is going wrong, you get into the mode of start replacing things one by one and then changing the IACV would be the first logical choice [Your mechanic may be at this point].
Salim
sorry for the late reply. i could not log onto this site for 2 days for some reason
i've pretty much explained everything that was done by the mechanic who is looking at the car to diagnose this. he's followed the diagnosis procedure as described in the shop manual and the IACV is not closing in accordance to the tests required (ie. ignition on without starting, and observe if the valve cycles). it's taken the mechanic 4 hours to reach this point
the idle has been "good" up to now. at most, it's a bit low at time, especially if all the accessories are on (except for the a/c, which raises the idle). when this first started last month, the shift points seemed off, and sometimes i wouldn't get overdrive/4th. and then there was the big clunk when coming out of park and between reverse/drive. i mistakenly thought it was the beginning of transmission problems, but when i brought it to the mechanic he saw right away there was something wrong with the idle.
does anyone know if in order to change the IACV, does the throttle body have to be removed?
Last edited by Benjamin T; Nov 15, 2009 at 10:17 AM.
CL Community Team
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From: Miami, Florida
Yes and know. The manual calls for it, but I've known others who have been able to get at the four screws directly underneath the throttle body and behind the black piece. In that diagram above you can see one of the screws at the bottom of the picture, if you're folloing along from the service manual it's in the SFI section, page SF-43. Again, you'd need a very small phillips head and it can be a PITA, but yes, it's possible to do without removing it.
Driver School Candidate
Joined: Oct 2013
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From: ca
i have a idle problem too. i just changed my spark plugs and cleaned my throttle body. and now when i start my gs300 in the morning it idles around 1800rpm. it takes 7 minutes to idle to 900rpm. how can i readjust the fast idle?
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