Need some help from my fellow forum members!

I have a 2018 Lexus RC300 turbo (awd). Current Mods: OVTune, TTi Muffler Delete, Injen Intake, PPE Catless Downpipe, Invidia Midpipe and Invidia Axle Backs.

Previously when I had a BMS Stage 1 tune, TTi Muffler Delete, Injen Intake, PPE Catless Downpipe, Invidia Midpipe, stock axle backs, I noticed a weird noise while accelerating. When accelerating it sounded like the car was sucking in air, then stopping, then starting again. I would hold the pedal steady and it sounded like I was tapping the gas pedal.

Today I finally installed my Invidia axle backs. I flashed my car with the OVTune a few weeks ago and the car ran great. While driving today, the car felt sluggish at low RPMs. When accelerating from 2k to 3k RPMs, definitely heard the car going wurrr wurrr wurrr, then on the freeway while stepping on it from 4k rpms and up it did the same. This was all in auto.

When driving in manual, it's not as noticeable unless I'm under 3k rpms. While driving, a CEL came on for a P0001, code for an error with the fuel volume regulator control or wiring. I cleared it but it came back about 40 miles later. I Googled what a P0001 code is and from the sound of it, it's what I am experiencing with the car feeling like I'm tapping the gas pedal when I'm holding it steady.

I can't find a diagram for our cars, so I was wondering if anyone can help me identify what to look at to verify if wires or parts are damaged? I want to try to troubleshoot myself before I take it to a shop but I'm not sure what I am looking for. Going to the dealer is unfortunately out of the question since I am modified with so many bolt ons.

Edit: Forgot to mention, when revving from neutral or park, everything seems fine, no hesitation or issues.

 

Looks like this might be a service bulletin related issue for the vacuum regulator valve. I hope this is it.

 

Video/Sound Clip

https://i.imgur.com/3ORgERx.mp4

 

Bingo, Thats it. This was a prominent issue on the 3IS 200T/300 Models. Theyll replace it under warranty at dealer, but they might try to decline it do to your intake.

 

bought the parts. Installed it but haven’t driven yet.

what’s odd is this doesn’t seem to be an issue for rc200t/300 that I’ve seen. Mainly an is200t issue.

 

I think the reasoning for that is the limited market the RC reaches, and the even more limited group of people who use club lexus on the RC side. But im glad you got the solution from the IS side!

 

yeah that’s fixed but unfortunately I still threw a CEL for p0001 again.

this refers to wiring or an open circuit. I am unable to find any problems visually.

 

Perhaps your MAF sensor has been damaged in the process of intake installation and removal? I feel like youd be getting more/different codes for that, including trac/vsc.

 

I don’t think it’s related to the MAF sensor. It’s a throttle or fuel volume issue. It’s an electrical issue for an open circuit.

it only started happening after I got my axle backs in. I’m on the OVTune and will reflash to stock and see if a Lexus repair shop can trouble shoot it.

 

When the CEL came back. I reset it. Reset my trip odometer. CEL came back in 14 miles. This seems about right as it came back after short drives.

This time instead of resetting the CEL, I reflashed back to the stock tune. 18 miles later, no CEL. I have an appointment to do an oil change at a well known independent Lexus repair shop for an oil change, so I'll have them check things out while I'm there.

 

CEL Gone. Back to normal operating procedures

 

I have the same problem...its the diverter valve..it wont hold boost pressure..I have taken out my diverter valve and check. The factory spring in the diverter valve is so weak.
when stepping at 2k to 3k rpm you will hear boost leak..
Now I block that diverter valve..and omg it is so fast now.
I could hear turbo fluttering..lol..many people says turbo fluttering noise is bad...I have done many research ..it wont harm our engine..the turbo just chopping back pressure.

 

My problem was the vacuum regulator. Turned out it's a common problem for 8AR-FTS motors. Replaced it and the hose and all my problems went away.