Editing Openai/69556a65-a290-8002-a217-eebca2e0b967


{{DISPLAYTITLE:Lexus RX 350 RPM Issue}}

''This conversation was exported from ChatGPT''<ref>{{cite web|title=Lexus RX 350 RPM Issue|url=https://chatgpt.com/share/69556a65-a290-8002-a217-eebca2e0b967|publisher=ChatGPT|access-date=2026-01-01}}</ref>

== gpt-5-2 ==
=== User: 2020 Lexus RX 350 F-Sport with over 47K miles and recently noticed that on occasions when I may need to accelerate and … ===
2020 Lexus RX 350 F-Sport with over 47K miles and recently noticed that on occasions when I may need to accelerate and it will start to redline and temporarily get stuck and not drop back down to normal rpm’s .

=== Assistant: That behavior on a 2020 Lexus RX 350 F-Sport 47k miles is not normal and usually points to a transmission or throttle c… ===
That behavior on a 2020 Lexus RX 350 F-Sport (47k miles) is not normal and usually points to a transmission or throttle control issue, most commonly related to how the 8-speed automatic is managing shifts.

Below are the most likely causes, starting with the most common for this model/year.

==== Most Likely Causes ====

===== 1. Transmission Hesitation / Shift Logic Issue (Very Common on RX) =====

Lexus RX models (2019–2021 especially) are known for:
* Delayed upshifts
* RPMs climbing to redline
* Transmission “holding” a gear too long before finally shifting

This often happens:
* During quick acceleration
* When merging or passing
* After slowing and re-accelerating

📌 Why it happens
* Transmission software struggles to decide which gear to select
* The ECU thinks you still want maximum power
* More noticeable in Sport or Sport+ mode

✅ Fix
* Lexus TSB (software update) often resolves this
* Dealer reflash of the transmission control module

===== 2. Throttle Position Sensor or Electronic Throttle Body Issue =====

If the car:
* Revves high
* Doesn’t immediately respond when you lift off the gas
* Feels like it’s “stuck” revving

This could be:
* Dirty throttle body
* Faulty throttle position sensor
* Accelerator pedal sensor lag

✅ Fix
* Throttle body cleaning
* Sensor recalibration or replacement (if faulty)

===== 3. Torque Converter Not Locking Properly =====

A failing or slipping torque converter can cause:
* RPMs to flare upward
* Delayed power transfer
* RPMs staying high even when speed isn’t increasing much

📌 Often intermittent at first, then becomes frequent.

⚠️ More serious if ignored.

===== 4. Transmission Fluid Condition =====

Even though Lexus markets it as “lifetime fluid”:
* At ~47k miles, fluid can already degrade
* Old fluid can cause erratic shifting and RPM flare

✅ Fix
* Drain-and-fill (NOT a flush)
* Lexus Type WS fluid only

===== 5. Drive Mode Effect =====

In Sport / Sport+:
* Transmission intentionally holds gears longer
* RPMs stay higher by design

📌 If this happens in Normal or Eco, it’s more concerning.

==== What You Should Do Next (In Order) ====

===== Step 1: Note the Conditions =====

Tell the dealer:
* Which drive mode (Normal / Sport / Sport+)
* Happens when warm or cold
* Happens during passing / merging
* How long RPMs stay high

===== Step 2: Ask Dealer to Check for TSB / Software Update =====

Specifically request:

: “Check for transmission ECU or powertrain software updates related to shift hesitation or RPM flare.”

This alone fixes many RX complaints.

===== Step 3: Request a Transmission Diagnostic =====

Ask them to check:
* Live shift data
* Torque converter lock-up
* Throttle input vs RPM response

===== Step 4: Consider Transmission Fluid Service =====

Even if Lexus says it’s lifetime, many techs recommend:
* Drain & refill at 50–60k miles

==== 🚨 When It’s Urgent ====

Go to the dealer ASAP if you notice:
* RPMs stay high even after lifting off gas
* Harsh shifts afterward
* Burning smell
* Check engine or transmission warning

==== Bottom Line ====

✔ Most likely cause: transmission software or shift logic
✔ Good news: often fixed with a software update
⚠️ Do not ignore — prolonged RPM flare can damage the transmission

If you want, tell me:
* Does it happen in Normal mode?
* How long do RPMs stay high (seconds)?
* Any warning lights?

I can narrow this down further.

== References ==
<references />


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