In acceleration, the boost pressure will start to fluctuate going up and down, you can also hear the turbo whistle go up and down. Lexus has had my car, supposedly replaced fuel injectors, check the computer and no error code are found.

Note: car is RC200T 2016 equipped with BMC in cabin air filter.

 

how many miles do you have on ur RC?

 

Dear ekimhey thanks for your reply.
Just 16016 km

 

That is pretty crazy to see the turbo gauge act that way. I've had several cars with a turbo over the years. The only thing close was getting the turbo replaced in my 88 Mitsubishi Starion under warranty. The boost was not what it should be and at WOT there was a little oscillation of the max boost but not as bad as yours. The dealer who replaced the turbo did not check / adjust the waste-gate (as they told me when I took it back). I dont see how that could be your issue unless the turbo is going out and the failure is related to the waste gate.

 

Thanks louczar.
I hope they will replace my turbo also. And the funny part in my story that is I own that car for less than one year now 👎🏻

 

could be just the boost signal to that gauge. I doubt your turbo can Fluctuate boost like that

 

No way because even the car will start jerking during that’s operation.

 

Did you figure it out?!! Mine is doing the same and I want to fix it!!! Please tell me what you had to do!!!

 

It was the vacuum regulator valve

 

Vacuum regulator, there's a service bulletin for it. Take it in to get replaced, the newest bulletin replaces the hose.

I had the same issue but fixed it myself.

 

so it’s the vacuum regulator or just the hose? And what’s a service bulletin lol

 

First service bulletin was to replace the regulator. Second service bulletin added the hose + regulator.

Service bulletin is a notice from Toyota/Lexus for dealerships to service these cars for free repair for known faulty parts. It takes a lot for them to happen to become a service bulletin, fortunately enough for us RC owners, the IS vacuum regulators have failed enough to make it a bulletin. This seems to be an issue on a lot of 8AR-FTS motors. Some IS owners have gone through several regulators.

Unfortunately for me, my car is pretty modified so I can't take it in for the free repair so I had to pay out of pocket and swap it out myself.

 

I see okay.
My car has a rebuilt title, so they won’t do it for me either. Should I just replace the regulator or the hose as well?

 

Replace both. Check the IS forums. There’s links of what to buy.

 

I had the same problem..but I didnt replace the regulator valve.I took out the bypass valve and close it up. And omg it boosted so nice..never had a leak anymore. Pple say it's bad..it will make the turbo to spin backward..i have done many research and it will never spin backward instead the turbo will chop the air. It will make a pigeon noise. I have driving with the bypass close for 6 months now..nothing happen no errors code. I really love it ..I never have a leaking boost pressure. But do it at your own risk