Idle is very finicky, but very different from CEL causes. I always suggest eliminate/fix CEL causing codes, isolate changing electrical + mechanical load and then focus on idle. There are know issues like IACV. dirty throttle body (clean makes it better, but usually does not cause erratic idle hunting). Proper fuel pressure and properly working injectors are pre-requisite for steady idle.

The reason idle is finicky as the combustion is controlled by the ecu closed loop process in a least engine load condition. If you have minute vacuum leaks the closed loop gets out of whack. I had a friend who's caddi which spent most of the time in air (on jacks) had an intake rip and it only opened up when the engine tilted under torque. So as engines age there are number of places where such a thing can happen.

I am suggesting to fix the high probability items. Just cleaning will not be enough as the slug motion needs to be free.

Salim

 

For sure, I’ll keep you guys updated. Is this a problem with the ES300’s as well with the same engine?

My mothers 2004 ES330 with the 3.3L V6 had 213,000 miles on it when she sold it, and that engine was still buttery smooth. It was very quiet and drove extremely well too.

So this seems unacceptable for a Toyota, and especially in a Lexus with the rough idle and vibrations.

If a new IACV doesn’t work fixing the issue, then I will suggest to my mother to take it to a shop so they can do a full diagnosis on it.

If the repair to fix the issue is higher than what the car is worth, then I will recommend her to just sell the car and get something else. Possibly a newer RX with the 3.5L V6 which is an awesome engine.

Because dealing with a rough idle all the time is simply not comfortable to drive and has gotten old very fast. I also think of possible engine damage and the motor mounts wearing out faster than normal with the constant engine vibrations.

 

The problem existed long before any CEL. It's done it the whole time I've owned the car and have already been through all this.

 

Does the idle problem exist in majority of the cases? The answer as far as I can say is, no. IACV acting up, that has been reported around 65-75K miles. Proper cleaning has remedied it and in some cases the IACV had to be replaced.

Intermittent leak in the plumbing of the air [also referred to as injection of un-monitored air in the system] in the intake will result in erratic idle speed.

My suggestions may not fix the problem but will address a common observed problem.

Salim