o2 sensor Test

[suren2485]

I'm driving an e39 523i with M52TUB25 engine. right now the issue i'm experiencing is bad fuel economy and poor low end torque.

Replaced parts:-
idle control valve
vanos seal
spark plugs
ccv valve and all the hoses
intake cam sensor
exhaust cam sensor
Airflow sensor
crank sensor
fuel tank breather valve
fuel filter
Disa valve

But the issue is still there, i suspect its the o2 sensor thats not giving proper air fuel mixture info to the ECU. but before i replace the o2 sensor any way to test it.

I so notice petrol smell from the exhaust when idling.

Any advice would be appreciated


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[Bhu]

I'm driving an e39 523I 2001 model. Almost the same problem as you, there's fuel smell near the left rear wheel area. Engine idling can be rough at times and then okay. Car doesn't accelerate when I floor the pedal. It'll be stuck at 20-30km/h and after a while it will be ok. If you do find the problem. Please do share. Thank you.

 

[suren2485]

I'm driving an e39 523I 2001 model. Almost the same problem as you, there's fuel smell near the left rear wheel area. Engine idling can be rough at times and then okay. Car doesn't accelerate when I floor the pedal. It'll be stuck at 20-30km/h and after a while it will be ok. If you do find the problem. Please do share. Thank you.

I think i found the issue, but still in the mids of confirming, did you change the throttle cable or removed the throttle body ? for drive by cable you need to readjust the throttle cable using an obd tool once done reset the adaptive value for the throttle body, i did this and there is a major difference but no 100% so far 70% issue resolved

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[Bhu]

The problem just just went away a few days after i posted it up here. The only thing i did before all that happened was switching the fuel from shell to caltex but i doubt that's the reason.
Could have been water in the fuel tank? I have no idea, just glad its working fine again. Did you manage to your solve the problem on yours?

 

[jarance]

I'm driving an e39 523i with M52TUB25 engine. right now the issue i'm experiencing is bad fuel economy and poor low end torque.

Replaced parts:-
idle control valve
vanos seal
spark plugs
ccv valve and all the hoses
intake cam sensor
exhaust cam sensor
Airflow sensor
crank sensor
fuel tank breather valve
fuel filter
Disa valve

But the issue is still there, i suspect its the o2 sensor thats not giving proper air fuel mixture info to the ECU. but before i replace the o2 sensor any way to test it.

I so notice petrol smell from the exhaust when idling.

Any advice would be appreciated


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High fuel consumption could be due to many thing. You have change almost everything to be change.

Do a engine compression to check whether there is leakage due to worn out valve seal, piston rings etc.

Another thing to consider is to check the fuel pressure at the fuel manifold. Ensure that it is 3.5bar.

I have change my fuel pump (not original) to work at 4.0 bar and the fuel filter pressure regulator give a constant
pressure. It manage to bring my "fuel consumption" back to normal (10.2L/Km). Used to be 14L/Km before I replace the pump.

Previously, I got the OEM pump from Auto Bavaria spare part shop. After using for 3 months, I change the pump with a pump
that I bought from aliexpress.

 

[jarance]

btw, you can test the O2 sensor or lambda sensor using INPA diagnostic tool.
If the sensor is faulty, the error will show you. It also will give you readings for the
2 sensors before the cat. Forget the reading from the O2 sensor after the cat.
They are for monitoring purpose.

The sensors before the cat is for regulating.

 

[suren2485]

High fuel consumption could be due to many thing. You have change almost everything to be change.

Do a engine compression to check whether there is leakage due to worn out valve seal, piston rings etc.

Another thing to consider is to check the fuel pressure at the fuel manifold. Ensure that it is 3.5bar.

I have change my fuel pump (not original) to work at 4.0 bar and the fuel filter pressure regulator give a constant
pressure. It manage to bring my "fuel consumption" back to normal (10.2L/Km). Used to be 14L/Km before I replace the pump.

Previously, I got the OEM pump from Auto Bavaria spare part shop. After using for 3 months, I change the pump with a pump
that I bought from aliexpress.

I'm using the same pump as the original Pierberg, like you said could be inconsistent fuel pressure, i changed the fuel regulator but no improvement.

i did compression test and all good, if valve seal is worn it will consume black oil correct and will have white smoke at first startup but i don't have such issues.

I will do a fuel pressure test to see if the pressure is consistent and if there is any drop. Appreciate your input man. [emoji2][emoji1474]


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[suren2485]

btw, you can test the O2 sensor or lambda sensor using INPA diagnostic tool.
If the sensor is faulty, the error will show you. It also will give you readings for the
2 sensors before the cat. Forget the reading from the O2 sensor after the cat.
They are for monitoring purpose.

The sensors before the cat is for regulating.

When i read online the issue sometimes if the o2 sensor is not giving proper values it will not trigger the error unless the o2 sensor is completely dead. i don't have much knowledge to read the proper value for o2 sensor when high rev and idling hehehe


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