2002 ES300 Bucking

[02ES300Jeff]

INTRO

Hi all, I have an ES300, and ever since I got it, the engine starts bucking when it has been running for a while and/or I floor it.

THE PROBLEM

What specifically happens is when I accelerate, before it shifts into second or third, (it only seems to have problems with these gears) the RPMs spike to 5,500 to 6,000, the car slows way down, the engine seems to buck (it feels like I hit a speed bump going about 30mph). 

POSSIBLE COINCIDENCE 

The bank 2 (front) catalytic converter code starts to show whenever this happens. I don't know if this is a coincidence, but it's frustrating. I see the problem isn't the catalytic converter because I bought a new one and put it on, and it didn't fix the problem, so I cleaned the old cat and put it back on. after that, the code for the catalytic converter didn't come back on for a while. 

WHAT THE MECHANIC SAID

The mechanic said that it was most likely either the transmission or the catalytic converter. I mentioned knock sensors but he said that he has never had a knock sensor not throw a code when it died.

WHAT I DID

My friend had the same problem in his ES300 that was from the previous generation, and he said that they replaced the knock sensors and fixed the problem, even though the dealership told them it was the transmission. So I replaced the knock sensors and all the gaskets we took off in the process. 

THE FIX

It seemed to work, I took it on the freeway and kept flooring it to get the engine hot, and it didn't buck when I had previously tested it, and it failed, with the new catalytic converter. So to make sure, I took a drive that was pretty much the same drive I had taken the summer before when I realized this was a big problem. This time, with the engine only resting about an hour or two before I drove back, the car had no issues. all seemed well in the world.

THE PROBLEM RETURNS

the other day I wanted to race my friend, and for the first time since I had tested the car on the freeway, I floored it. but this time it bucked again when it was trying to shift into second or third (I can't remember which one) and a few days later the same cat code I had before appeared.

POSSIBLE FACTORS

since I got the car, it has jerked whenever I put it in reverse

I think there are 5 motor mounts in the car, and 3 or 4 of them are bad

the power steering pump was leaking very slowly for a while, which made me burn through belts very fast (fixed now)

 

 

I appreciate any tips that you guys have for diagnosing this, I want to get this fixed but i don't want to pay a mechanic an insane amount of money to diagnose it and be wrong. Thank you all for your help.

Edited May 30 by 02ES300Jeff

[RX400h]

Quote

The issue you’re experiencing with your Lexus 2002 ES300 could be due to several factors. Here are some possibilities based on the information you’ve provided and some additional research:

1. Transmission Issue: As your mechanic suggested, the problem could be related to the transmission. The bucking and RPM spike before shifting into second or third gear might indicate a transmission problem.

2. EGR Valve: A faulty EGR (Exhaust Gas Recirculation) valve can cause the engine to buck. The EGR valve helps to reduce the engine’s exhaust emissions. If it’s not functioning correctly, it can cause performance issues, including bucking during acceleration.

3. Fuel System: Issues with the fuel system, such as dirty fuel injectors or combustion chamber deposits, can cause power loss and sluggish acceleration. A fuel system cleaner that contains polyether amine (PEA) might help if this is the case.

4. Vacuum Leaks or Intake Issues: Vacuum leaks or problems with the intake plumbing can also cause the engine to run rough. Inspecting these components for leaks or cracks might be worthwhile.

5. Catalytic Converter: Even though you’ve replaced the catalytic converter, it’s worth noting that issues with this component can cause similar symptoms. However, since the problem persisted after replacement, it’s less likely to be the cause.