rik881

Hi, i have a small problem with my S500.

It runs and drives normally but i get system too lean codes for both banks. I checked everything i know off. Vacuum is fine. Fuel pressure 58 psi. Starts and runs normally. LTFT are like +28 percent for both banks and they don't move. STFT is zero. I have also tried another maf sensor. Where else should i look?

Thanks in advance for any help.

ibeforreal

No CEL? how old are your oxygen sensors?

rik881

I still have the original O2 sensors. I had check engine, i resetted it and did not come back yet. I did not drive a lot, i don't want to break anything. Should i try to change front and rear o2 sensors?

rik881

Does anyone have the part numbers for the front o2 sensors on a W220 s500 2003? 0005408117 or Bosch 16274 i think should fit. Can anyone confirm this?

wallyp

If your upper-range hearing is good, get a 4' piece of small plastic or rubber tubing. Stick one end into your best ear, and use the other end as a probe to detect the hiss of a vacuum leak all around the intake, MAF, etc. Careful around hot and moving parts!

Using the long tube as an extension on a stethoscope works even better.

ibeforreal

Here are the Oxygen Sensor part numbers on my 03 S500 taken directly from epcstartek. When I replaced my upstream sensors I was able to get Bosch brand from Advance Auto/Carquest. It is a relatively easy job. Just get that funny looking socket with the cutout on the side designed specifically for 02 Sensors. The socket is about $8 from Harbor Freight.

rik881

@ Wallyp i think i can scratch vacuum from the list since i used a vacuum gauge and it stayed in the green part meaning vacuum is fine. If the vacuum gauge shows good negative pressure i guess i'm safe to say vacuum is not the problem.

@ Ibeforreal I also doubt the o2 sensors being the problem. The readings seem fine. I used the graph on my scanner to check both and both seem fine.

I also thought about the cats being stuck but that should not be the problem as well since the car has only 20k miles.

I had the car running for half an hour stationary waiting for the obd codes to come back but nothing. Fuel Trim don't move a bit. STFT for both banks stays between 0 and 1.6 and LTFT for bank one is 28.7, bank 29 something. I'm afraid to drive the car like this even though everything seems normal. Starts fine, runs fine. Shakes a very little bit. A coin would not stay on it's side but nothing to worry about.

I once had a misfire cil 1 problem which was caused by a vacuum leak from a small hose inside the intake.( nothing to with my new problem i suppose)

I have ordered cheap aftermarket o2 sensors and maf sensor although i doubt they will be the problem.

What is the correct fuel pressure anyway? I can't find this, and yes i searched. Finally one last question, can the PCV have anything to do with my fuel trims being way too lean?