Engine Noise When Cold - 2005 Ls 430

[puppo420]

I have a 2005 LS430 that i bought a month ago. it has 25K miles. I switched from dino oil to Mobil 1 at last oil change. I recently noticed an engine noise which comes when engine is cold and goes away when its warm. Its not loud but it is annoying to me. The noise is like "shook shook shook shook" and seems like something to do with a bearing or pulley on low Rpm when cold. It goes away magically when engine is warm. It is more noticable in parking garage or when windows open. I tried turning AC on and off thinking its compressor but to no avail. I hate this noise and i know its not Lexus like. When warm, its very quiet. i have tried to listen where the noise comes from but to no avail. It does not seem like EGR/Valve/lifter noise. I took it to dealer and left overnight to look for this noise. Next morning they started car in front of me and it did not even come that day. Also noticed this noise come when car is parked on a little slope. The noise is lesser if car parked on a flat surface overnight. Something to do with oil or pump ? i am going nuts.... Please help :)

[nc211]

it happens, usually if you start the car cold, move it slightly, then turn it off and don't start it again for like 24 hours. And if it's on a slope with the front end facing downward, it's enhanced. I think it's the fuel injectors putting in too much fuel when you turn the car off, then when you start it up, there is that extra fuel sitting on the pistons. Kind of acts like it's flooded?

I started my 95 the other, after it sat for about 5 days, and did it ever shook, shake, sputter and rutter for about two or three minutes, then it settled down.

One thing to consider though is the oil filter you use. There has been conversation on here regarding certain oil filters that might not hold enough in it's reserve for a cold start on synthetics. I use OEM filters myself.

[puppo420]

it happens, usually if you start the car cold, move it slightly, then turn it off and don't start it again for like 24 hours. And if it's on a slope with the front end facing downward, it's enhanced. I think it's the fuel injectors putting in too much fuel when you turn the car off, then when you start it up, there is that extra fuel sitting on the pistons. Kind of acts like it's flooded?

I started my 95 the other, after it sat for about 5 days, and did it ever shook, shake, sputter and rutter for about two or three minutes, then it settled down.

One thing to consider though is the oil filter you use. There has been conversation on here regarding certain oil filters that might not hold enough in it's reserve for a cold start on synthetics. I use OEM filters myself.

It happens every morning and the car will sit overnight in the parking garage. The slope is towards the left side and very little one. I would say may be 3-5 degrees. The car does not sit more than 12 hours at night. I have a feeling its related to my oil change to Mobil 1. But this noise stays for 10 minutes and vanishes completely when engine is warm. It comes back again if the car sits for 5 hours like in my office and does not cool down completely. I use OEM Toyota filter. The one that ends in D3. It has Mobil 1 5w-30 in it now. It does not seem to be an injector problem as i dont move the car once its parked. Does it take 5 minutes for OEM filter to fill up???? The noise stays till engine has reached middle point on the coolant guage. I cannot go back to dino oil to see if it is the oil because i think its no recommended at all..... what else can I test ? Is it piston slap coz they expand when engine gets hot ????

This noise is best described as " When you turn on the engine and it idles, there is a faint noise that comes from inside the engine compartment when the belts turn...like a constant "shook, shook, shook" but not extremely loud can notice it only when idling and when driving slow speeds...at higher speeds engine runs smooth... " I copied this line from http://www.automotiveforums.com/t252138-ne...0_miles___.html but this guy has much more severe problems than me. My Ls430's engine is clean and no problems what so ever except this annoying noise which haunts me in my sleep toooo :( as i am a perfectionist or at least try to be and even a little thing bothers me :( Thanx NC211 what else can you suggest .....