High idle when hot

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May 31, 2005
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My Lexus LX450 idles at 1800 when hot. I'm having trouble adjusting. Could there be other problems causing this?
1800 is high enough that I'd really carefully check all the cables, linkage, return springs, etc.

Hard to get an idle that high just from a vacuum leak, etc. More likely something's keeping the throttle plate from completely closing.
 

LandLocked93

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Yeah I fought this issue for a while, from a "cheapest thing first" approach.
Adjusting works to a point. Generally what happens in that case is that you have to adjust the cable "up" at cold start to get good idle, then back "down" to get good idle when hot.

Ultimately I determined it was (non-fixable) drag in the cable and pedal assy ('93 model)
FWIW here are the part #s, should get you close for Lexus unit.
1 - 78120-60080 - Rod Assy, Accelerator Pedal (vintage part was unspeakably stiff to depress, very worn pivot (300kmi))
1 - 35520-60110 - Cable Assembly, Throttle (vintage part showed obvious signs of significant deterioration on the outside)
 
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1800 is high enough that I'd really carefully check all the cables, linkage, return springs, etc.

Hard to get an idle that high just from a vacuum leak, etc. More likely something's keeping the throttle plate from completely closing.
Thanks for the assessment. I will re-check everything. I agree, I think something is keeping the throttle plate from closing. The strange thing is this only happens when it is hot, like hot outside, in hot weather.
 
Joined
Feb 9, 2022
Messages
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San Jose
Yeah I fought this issue for a while, from a "cheapest thing first" approach.
Adjusting works to a point. Generally what happens in that case is that you have to adjust the cable "up" at cold start to get good idle, then back "down" to get good idle when hot.

Ultimately I determined it was (non-fixable) drag in the cable and pedal assy ('93 model)
FWIW here are the part #s, should get you close for Lexus unit.
1 - 78120-60080 - Rod Assy, Accelerator Pedal (vintage part was unspeakably stiff to depress, very worn pivot (300kmi))
1 - 35520-60110 - Cable Assembly, Throttle (vintage part showed obvious signs of significant deterioration on the outside)
Thank you, Good info. I can see where this could be the case. And yes, I have been doing the "cheapest thing first" approach.
 
Joined
Jan 12, 2016
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Australia
when it does the high idle have you tried turning it off, disconnecting the cable from the throttle and restarting?

this will tell you if its a sticking or incorrectly adjusted cable if the idle comes back down or if it stays at 1800 id be looking at removing and cleaning the throttle and IAC valve & port
 
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Jul 25, 2021
Messages
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Toronto, ON
Had the same problem, my idle would float up to 3.5k! Put your finger on the throttle body and pull it back to idle and see if the idle lowers to 500…if that’s the case it’s your throttle cable (take a pic and post it here). For now just tip your foot under the pedal to loosen up the cable.
 
Joined
Jun 26, 2004
Messages
2,165
Location
east coast Canada
Yeah I fought this issue for a while, from a "cheapest thing first" approach.
Adjusting works to a point. Generally what happens in that case is that you have to adjust the cable "up" at cold start to get good idle, then back "down" to get good idle when hot.

Ultimately I determined it was (non-fixable) drag in the cable and pedal assy ('93 model)
FWIW here are the part #s, should get you close for Lexus unit.
1 - 78120-60080 - Rod Assy, Accelerator Pedal (vintage part was unspeakably stiff to depress, very worn pivot (300kmi))
1 - 35520-60110 - Cable Assembly, Throttle (vintage part showed obvious signs of significant deterioration on the outside)
Did you notice peddle was still to initially move?

Mine is stiff to get from idle position, once it “let’s go” it jumps. With cable disconnected from both ends cable is smooth as butter.

Never thought of checking pedal linkage pivot🤔

I will now
 
Joined
Jun 26, 2004
Messages
2,165
Location
east coast Canada
Thanks for the assessment. I will re-check everything. I agree, I think something is keeping the throttle plate from closing. The strange thing is this only happens when it is hot, like hot outside, in hot weather.
What is your cold start rpm? It should only go to roughly 1200 rpm for a minute or less then slowly drop to its 650 idle rpm.

Mine use to jump to 1800 for a few minutes at cold start.

After throttle body cleaning and decarborizing the IAC problem fixed.
 
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Feb 9, 2022
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Thanks everyone for your feedback. I do think the throttle cable is worn and needs replacement. I also want to clean the IAC. It looks to me that I will have to remove the throttle body in order to remove the IAC. I was trying to be lazy and just remove the IAC but I can't see any way to remove the lower screw. Any suggestions or do I just bite the bullet and remove the whole throttle body?
 
Joined
Jan 12, 2016
Messages
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Australia
Thanks everyone for your feedback. I do think the throttle cable is worn and needs replacement. I also want to clean the IAC. It looks to me that I will have to remove the throttle body in order to remove the IAC. I was trying to be lazy and just remove the IAC but I can't see any way to remove the lower screw. Any suggestions or do I just bite the bullet and remove the whole throttle body?
remove the TB its the only way to clean it properly, especially the back of the butterfly and ensures all the crud doesnt go into the intake manifold.
it also makes removing the IAC screws easier, especially the bottom one
The IAC screws are easy to round off the phillips slot so be sure to use a quality screwdriver that fits snug in there.

be sure to tape off or block the intake with a rag so you dont drop anything in there as well
 

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