alsuwaidi

Hi there,

I've been having acceleration problems with my 2008 LS 460 since last year.
At first, I thought that the problem was with the transmission since I would feel a jerk coming from the transmission side whenever I'll try to accelerate hard.
I've decided to do multiple changes to the ATF with a fully synthetic ATF fluid that is compatible with Toyota WS. I've done 5 changes every time draining and refilling around 3.4 quarts. It helped only a little bit but you could still feel the jerk from time to time. Sometimes the car would accelerate very smoothly and sometimes it is as if the car is in Limp mode and it jerks hard.

Next, I've decided to clean the cats especially since the car has north of 300k miles. This helped a lot the acceleration was very smooth but I still would feel the jerk from time to time and when it happens the car is really weak and barely accelerates.

Last week it was time to do brake fluid replacement for the LS so I borrowed a scan tool to do the bleeding. After finishing I took the car for a test drive with the scan tool hooked and checked the live data. I was surprised to see that the Long term fuel trim for bank 2 is +24% while bank's 1 long fuel trim was -8%.
I knew I had to look at either the O2 sensors or the catalytic converter Temps. The Cats' Temperature was normal.
Upon checking the O2 sensor, Bank 2 sensor 1 was not giving any voltage reading at all. all other sensors were ok.

I took the car to a local shop to inspect it. He told me that the wire for the O2 sensor was cut. He fixed the wire and connected the sensor. Upon checking the sensor's voltage with the scan tool it was still not giving any reading. What surprised me is that no check engine light is illuminated. Not when the wire was cut and not now.

I've ordered a new sensor but the shop told me that Lexus might have replaced the part number as the new part is short and does not reach the plug area.

I am not sure what to do next & I think that this is the root cause of my acceleration problem.

Sorry for the long read. Any help would be appreciated.

BTW, the shop that ordered the O2 sensor used the VIN number to order.

swfla

iTrader: (1)

You may also have worn/damaged engine and transmission mounts contributing to the jerking sensation.

alsuwaidi

Thanks for the reply.

Engine & trans mount were replaced 30k km ago
I follow the maintenance schedule strictly.
Air filters were replaced 10k km ago
MAF and throttle body were cleaned recently.
injectors were cleaned and spark plugs were replaced in a specialized shop 45k km ago
Engine oil and ATF were replaced recently.
The fuel filter was replaced 60k km ago. We only use premium fuel here in UAE.

Anything else that could lead to this problem?

BTW was just checking the fuel trims. On Bank 1 where the sensors are good, the fuel trim keeps fluctuating between +3 to 0 to -3, but on Bank 2 the fuel trim is stuck at +19.5. I think ill take the car to the dealership but I am really busy currently.

MarciaJon

Have you resolved it?


alsuwaidi

Sorry for the late update. I've been really busy at work over the past two weeks, but managed to make a family member take it to the dealership. It took a whole week to figure out the problem.
I received a call yesterday from them, it seems that the car's ECU was modified by a repair shop that worked on the car last year.
Back then the car had VSC/ABS/Trac light with DTC codes of the same oxygen sensor circuit open.

That shop kept working on the car for an entire month. I remember the Mechanic at the shop calling me and saying that they didn't figure out why the DTC is showing since everything is working fine, but that they will solve the situation. It seems that they hacked the ECU somehow and made the O2 sensors give false readings to the engine. This is why it is not giving any check engine lights.

Now the dealership is recommending replacing the ECU, The whole engine harness, and all of the O2 sensors for 5800$.

I think I'll take the car to that same shop and push them to fix it since they started the whole thing.