Buffalo777

I have Lexus RX330 AWD, year 2004, made in Japan.
A couple of years ago I notice random vibration, which typically happens while the car is waiting for green traffic light, when automatic transmission is in the "Drive" position, and the foot breaks are applied.
I have a feeling that vibration comes from automatic transmission, though I may be mistaken.

It is really annoying. Any thoughts on the cause of this problem?

coolioe93

Sounds to me like you need a throttle body cleaning and fuel injector service. Is it worse with the ac on?

Buffalo777

Thank your for your suggestion.
After reading your comment, I turned off A/C while driving and noticed that vibration while waiting for green signals almost disappeared!

I have a question for you: what is the relation between throttle body or fuel injector from one side AND air conditioner from the other side?!
I googled this question out and could not find any answers.
Your explanation will be greatly appreciated.

TheGoodGuy

I have this same issue on two of these engines, diff vehicles. Subbed for the explanation. It drives me nuts. I noticed too that if you get off the brake for a second then reapply it lessens the shakes.

coolioe93

Air flows through your throttle body and intake manifold into your engine where combustion happens. Fuel flows through the fuel system and through the fuel injectors also into your engine where combustion happens.




Over time, as air flows through your throttle body and intake manifold, carbon and other debris get deposited into the walls of the throttle body and intake manifold. This causes turbulent air flow and a mismatch between how much air the engine gets vs. how much it "asks for". This leads to decreased engine performance and is felt by the driver as vibrations or shuddering of the engine. Similarly, over time, as fuel flows through the fuel system, deposits form on the fuel injectors, fuel lines, and even on the valves inside your engine. This also leads to decreased engine performance which is felt as vibrations and sluggishness to the driver.




These effects are most pronounced at low rpm's and high engine load such as when stopped at a stop light with the transmission in drive. I asked about the AC because when the AC compressor is on, it causes an increased load on the engine which will make the vibrations and shuddering even more apparent at a stoplight.




Cleaning the throttle body is easy and should take no more than an hour. I recommend removing it from the engine bay and cleaning it by hand so that you can get more debris out. Here is a video showing how to find the throttle body and how to clean it in a toyota engine (procedure should be the same for the rx330. RX350 is a little different - I'm sure you can find a video on youtube for it.).




https://www.youtube.com/watch?v=jno6cSDN47I




Cleaning the fuel system is more difficult. You can use a cleaner such as this one. Just add a full bottle to an empty fuel tank and fill the tank to full when you're at the gas pump. The cleaner will slowly work through your fuel system and do its best cleaning up any debris. If you've never done this before, then I would recommend buying two bottles and doing two treatments.




https://www.amazon.com/Chevron-65740-Techron-Concentrate-Cleaner/dp/B00092893E/ref=sr_1_4?ie=UTF8&qid=1511545299&sr=8-4&keywords=fuel+system+cleaner




Lastly, the intake manifold and valves in the engine can also be cleaned by using seafoam. This is a bit of a controversial product. Some say that it doesnt do anything and is "snake oil". However, I have used it over a dozen times in many different cars and it works wonders. It has fixed up sluggish performance, vibrations, and bad idling for me in many cars. To use the seafoam, you need to find a vacuum line or use a bottle that allows direct injection of a spray seafoam bottle into the throttle body of a car with the engine running. Use a whole can, shut the car off, let it sit for about 30 minutes and then drive the car around. You need a good number of hard accelerations from 0-60 to get all the seafoam and carbon deposits out of the engine.




If you are familiar with working on cars, then you can do all of the above for under $40 at home. However, if you've never worked on cars before, then a local mechanic should charge around 150-300 for doing all of the above (depending on where you live).




Last point - I think the above should fix your issues, but if they don't then you may need a motor flush (again a controversial procedure). If the above doesn't work, then I can do a write up about the motor flush which also cleans out the engine and decreases vibrations that have slowly built up over time.

Htony

Just have a complete tune up. Your engine is not running right. At any garage if they hook up scope, they'll ffigure out the problem very quickly.
Is the tach. needle fluctuating at idle?