Hello,

I have a new to me 2003 LS430 with 103k on it. The car is in great shape, upon buying it I: put in new air filter, cleaned the MAF and throttle body (both were a bit dirty). I also replaced the PCV valve. The PO recently changed plugs at a Lexus dealer.

I can't figure out what is going on, my car will idle at about 450 RPM when in Drive (in neutral it is normal, around 650 rpm). Furthermore, when I turn the headlights on, it idles at a normal 650ish RPM.

I am guessing I need to do a vacuum test on the valve cover gaskets right? Anything else you might try? At 450 rpm it vibrates and drives me nuts. I'd appreciate any and all thoughts.

Thank you!

 

Intake mix paths and throttle body likely need cleaned then recalibrated provided the valve covers are sealed and the PCV is working.

 

Normal behaviour, or at least mine and every one I drove did the same.
It's just the ECU responding to load and demand.

 

It's not normal, Mine doesn't change following proper intake off cleaning and a relearn

 

If OP opened the throttle plate with his hand during cleaning he may have messed up the calibration. This is explained in the throttle body cleaning thread. If I were him I would also inspect the transmission and engine mounts. Even when my car idles low there is no vibration. Also check the condition of the vacuum lines.

 

Sorry, my bad!
I was noticing the Rpm drop on mine when it was still in Fast Idle (drop from 1000 to 700rpm when drive is selected).
The vibration is definitely not normal and those RPM values are too low. Idle should be 700-800Rpm with the engine fully warmed up.