I may be going crazy here so I wanted to poll other LS owners on their cars idle. Prior to my recent timing belt job I recalled (perhaps incorrectly since the car is so new to me) that when my car was idling you could almost not tell it was running because it was so quiet. Now after my recent timing belt job (which was not without its problems and required me to manually turn the engine at the crank to find TDC) the car is running GREAT but now I hear the engine... not a true knocking or ticking per se but just louder.

The idle seems smooth, car runs great, the RPMs are very stable and I only "hear" the car when I am outside (still silent when in car) which adds to my confusion because perhaps my recollection of a silent idle prior to work was from inside car.

I do not recall exactly the idle rpm prior to the work but my guess was 6-700rpm and now its right at 900 which may be a factor (it definitely feels like its idling higher now). Could timing be an issue? I am worried that I may have done something when manually turning the crank (and yes I did turn it counter clockwise about 1-2 degrees when I overshot the mark before I knew that even that little of a CC movement was BAD.... )

So I ask, what does your car idle at (RPM) when warmed up and just how quiet is it (or should it be)? What possible damage could a minor counter clockwise manual crank do? (keeping in mind that I brought it back in time with marks perfectly before ever starting or cranking with key)

I am starting to think I am a hypochondriac when it comes to my LS :P

 

My car has idled at right around 750 after it is FULLY warmed up. Quiet from the inside an outside standing right next to the car. Maybe you have some kind of exhaust leak. Are you throwing any codes?

 

No codes and definitely not an exhaust leak, not that "type" of noise. Probably my imagination. Ill take a video if it keeps bothering me but I think 850-900rpm idle is a little high

 

depending on the time of year spring/ summer very quiet almost a hum. Late fall and winter I can hear it idling even after its warmed up right around 900 rpm.

 

depends on whether A/C is on or off. my 90 is about 700 A/C off and 850 with A/C on according to cluster needle, not professional gauge.

if you want the exact readings, get it read by OBD1 code reader

 

I couldn't tell what year LS400 the OP has, but if it is 1995 or later, and a US model, it has OBD2.

 

it might be injectors. i dont have an exhaust leak but i do hear rhythymic small tapping noise. now it could be valve lash (lexus manual states to check valve lash every xx miles). Mine coul dbe injectors and valve lash. its very very quiet, but if its idling in the garage with the overhead door just cracked open i can hear the faint tapping.

 

just make sure you're checking idle witht eh car in park or neutral, fully warmed up, a/c off.