checked my engine light at Autozone and the codes on my es300 1998 were:

1. P0300, P0301, P0303, P0305 (random cylinder misfire, cylinder misfire 1, 3, and 5).

2. P0171 - "system too lean- bank 1 (cylinder number 1 denotes bank 1)"

I had some recent repairs, which are: tuneup (spark plugs, ignition coil #2, ignition coil wires), oxygen sensor (bank 1 sensor 1).

i have visited several mechanics, none of them have pointed to a particular problem, basically they are trying to change most of the engine. Please share any tips that you have thx.

 

Try changing the coil wires as well.This helped with the misfire for me.

 

I would put money on the fact that the O2 sensor was misinstalled. When you are having multiple misfires and a System to Lean, that usually points to something like an O2 Sensor. Plus 1,3,5 are all Bank One Cylinders.

 

the codes were in place before the o2 sensor was changed. basically i had all of these ocdes plus the o2 sensor code simultaneously. so i have changed the o2 sensor thinking it would solve all the codes, but it didnt.

 

Well System to Lean means that the O2 sensor is reporting too much oxygen. That means either Your mixture is actually off or there is a sensor that is malfunctioning. I would check the Mass Air Flow sensor, which can cause a System to lean although I am not certain that would cause Misfires. Is the car actually running poorly? With 3 Misfires it would be running like crap, and just barely at all.

 

Ayroman, do you have an aftermarket intake system or K&N filter?

 

i dont know if i do, and dont even know how to check that.

 

You did your spark plugs right? I hope you checked gap even if pre-gapped..in transportation pre-gapped can get out of recommend gap. I had misfires on my Benz which only showed up at higher RPMs which I didn't know at the time it was detonation based from using lower grade fuel then recommended for my car. I bought new pre-gapped plugs and checked them prior to install and most needed to be re-gapped again. So check that they are definitely gapped correctly.

 

here is an update this this P0171, i have removed the code through the engine checking computer. Drove the car for abput 25 miles, and the check engine light popped up, i immediately drope up to autozone and checked for any codes, and the only code this time was:
P1133 ("air/fuel ratio sensor circuit response malfunction bank 1 sensor 1"),
But keeping in mind that i have changed my bank 1 sensor 1 O2 sensor just last a week ago. some symptoms are :the car hesitates and loses power from time to time.

 

Did you check my response above?

 

Hesitation or loss of power can be the spark plugs installed with wrong gap

 

thanks for your input, my spart plugs were changed by an experienced mechanic, at least thats what i think, along with the wires. I am not sure tho

 

The P1133 is a Lexus specific code and it appears related to your air/fuel O2 sensor. Did you have all 3 replaced or just certain ones? And did you use the Denso OEM O2 sensors?

 

i have only changed the bank 1 sensor 1 oxygen sensor (before ct converter), and yeah i bought it from Denso.

 

Hmmmmmm, ok, well, appears you had the proper one replaced. Here in Calif. we have to use a specific air/fuel O2 sensor, because of the strict Calif. emissions. There are two parts numbers for the O2 sensors, one is for Calif emission vehicles and the other is for non-Calif emissions. Hopefully, you have the right one for that ES300. Otherwise, dont know why your having a CEL for the O2 sensor if you got the proper one replaced. Keep us posted and maybe you might have to take it into a Lexus dealer or find a Lexus mechanic who can diagnosis the issue right away. Good Luck.