Poor Acceleration in lexus es300 2003

I have a lexus es300 I got in 2020 with about 200k miles on it. Car drives well with zero problems but recently I noticed an acceleration problem. I scanned with my obd and got p0330 for knock sensor, p0420, p0430 for cats and two other codes related to small leak of fuel vapor.

This acceleration problem presents as difficulty gaining speed, there seems to be few seconds delay in speeding up from a low speed like after a check point or afterenteringa highway to speed. I called my mech he inspected plugs and coils and said they’re bad I changed them all plus fuel filter/pump but this thing continued.

I requested they inspect the cats for blockage which was the case in the upstream bank and I had it emptied but this thing no stop.

I was confused. I ordered for new knock sensor plus the harness and I will fix them when they arrive.

Yesterday on the highway I took closer look at the rpm and noticed it freezes sometimes. When I step on the gas on the highway I hear engine sound increase but rpm does not go up and speed does not increase. The rpm seems to be stuck at 1.4 as I step on the gas. At this time it is stuck, I struggle to gain speed till after a while it surges forward and rpm starts moving up again. Gas milsge is 12mpg city and about 17 mpg highway.

I noticed that other cars tend to be faster after we all slow down to a speed bump and about to speed up as I will be struggling for that some seconds to gain speed. Sometimes i have to remove my feet on the gas and step on it again for the rpm to actually go up and I can attain upto 130km depending on the road conditions.

Sometimes too the rpm bounces back to 1 with my feet on the gas then it sticks at 1 for about 5 seconds then pushes upward as the car speeds up to high speed.

My problem is mechanics in my area do not understand anything I am saying but I know something is wrong with this car.

Does anybody have any idea what I’m missing?

It’s good to empty cats. Every so often.

A bad knock sensor on this car typically does not result in the poor performance you have.

You bought it 2 years ago with 200K, how many miles are on it now? Has any mechanic run a compression test? or a Fuel pressure test? Does the car use lots of oil?

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Where is your area ? Did you not pay for a shop to actually do a diagnostic to see what is the problem . As for not understanding , I am having a little trouble also. Throwing parts and guessing hardly ever solves anything.

The way you wrote this is a little confusing . . .

But it sounds like your automatic transmission might be slipping?


This is a bit confusing to me also. I know what I would do; or would have done during the plugs/coil change.
Run a compression test based on the age and 200k miles on it.

If the engine is on the way out of this world then none of the peripherals are going to help and it’s all a waste of time and money.

I can think of a number of lack of power possibilities but IMO making sure the engine is solid would be step No. 1.
Fuel mileage is poor and I do not think the knock sensor is going to cure this car’s ills.

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You need to find a good mechanic and let them diagnose the problem. From what you describe it should be fairly obvious.

If your RPMs are at 1 and 1.4 (X1,000) the transmission must be in a very high gear. That would explain very slow acceleration. Maybe it is not downshifting when you press the gas pedal.


It consumes oil after a long drive say 6 hours that i will have to buy one litre and add it but in normal daily minutes driving in the city, oil consumption is not a worry. Then, i have not run any compression test or fuel pressure tesy. I will enquire where to and do it.

I am in Nigeria. It is difficult to find mechanics that run on auto diagnostics. It’s only i read up my symptoms on Google and tell them what to do with basically spanner and screw driver. I took a mechanic on a long drive to experience exaclty this problem and he suggested throwing parts around and when the few i obliged him did not work, he said i should flush my transmission but no way i am going to let him do that.

Is it possible for this error to throw transmission codes on scan?

Okay. I will get the transmission checked. Thank you

I also want to add, for the two years i had it, i have never done any maintenance on the transmission. Now my mech suggested i flush the ATF and add new fluid but i am scared to do it to not cause more problems. My question is, can dirty transmission fluid cause this problem? Can i find a diagnostic code for this? I am very inexperienced on this and have no idea what to expect. Presently i feel no obvious transmission problems, car shifts into reverse, drive, neutral easily.

Why does mechanic think you need a trans service? What is rpm at 60mph? It should be about 2000

Don’t you have a dealer you can use ? Telling a mechanic what to do by looking on the web has a very poor chance of solving this problem .

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Remember, this is a Toyota Camry on the inside, nothing fancy. Maybe that’ll help you find someone that can work on it.

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With that kind of oil consumption I don’t see converters, O2 sensors, or spark plugs holding up very well.
Might check the PCV valve and hope for the best.

That “upstream bank” is an eye opener for sure…

Rpm at 60mph is above 2000. Mech mentioned a trans service after plugs and coils and fulel pump/filter did not reolve the acceleration delay and coupled with the fact that I’ve never done a trans service in 2 years bcos i have no issues with my gear