Odd Idle Issue
Lexus Champion
Joined: Oct 2019
Posts: 18,612
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From: Ohio
RPM in ls460 is ECU controlled, when there is any accessory load on the alternator (e.g. AC, lights, seat heaters, etc.) min RPM is raised from 500–>700-750.
My experience is smoothness at 500 rpm varies from a car to another. This is why many people pay attention to this phenomenon. When it is rough people raise concerns. When it is not rough, we don’t pay attention.
bottom-line, I agree that cleaning throttle body and MAF may improve idle smoothness at 500 rpm but all cars I owned dropped to 500 with no accessories.
My experience is smoothness at 500 rpm varies from a car to another. This is why many people pay attention to this phenomenon. When it is rough people raise concerns. When it is not rough, we don’t pay attention.
bottom-line, I agree that cleaning throttle body and MAF may improve idle smoothness at 500 rpm but all cars I owned dropped to 500 with no accessories.
Instructor
Joined: Oct 2005
Posts: 757
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From: GA
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Pit Crew
Joined: Jan 2022
Posts: 143
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From: MA
The throttle blade has a set position it rests at when at idle, if carbon builds up it doesn't have as much airflow resulting in the RPM drop when you put the load of the transmission on it. It avoids this with the AC/heated seats since the program knows demand will be high and it actually adjusts up off the "idle" position unlike when you put it in gear, this is why I am telling you to clean it and have it relearn if you want no load in drive/R to be correct.
Thread Starter
Pit Crew
Joined: Jan 2022
Posts: 143
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From: MA
Hfahamy, I will post results once I get a few moments between rain drops/work to do it! Hopefully in next few days. If for no other reason than to get some definitive data.
Instructor
Joined: Oct 2005
Posts: 757
Likes: 61
From: GA
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