E39 520i Touring fuel consumption

[secretwpn]

Hi guys!
Please excuse me for english in this thread,
mutta en puhu suomea hyvin vielä.

The question is what should be normal fuel consumption for pre-facelift 520 wagon (petrol engine, M52B20)? I get something like that:
highway: 9
mixed: 11-12
city: 13-14

Looks a bit too high, doesn't it? What do you think?

I am not too heavy on gas pedal, just normal family driving. Mostly drive alone though, short trips in city home-work-prisma-home.

Google says often O2 sensors are to blame, but AFAIK if O2 sensors are bad your idle won't be steady, and mine is pretty stable.
So changing the sensors blindly without knowing that they are indeed the source of a problem is a bit too much for me (I'm tight on budget at the moment)

Thanks in advance!

[Haatainen]

Is your car manual or automatic?

I had elevated fuel consumption on my 530iA, (10/13/17 l/100km). There was two separate causes for this: the turbine lock of the transmission was not working properly and the primary O2 -sensor of bank2 was faulty.

Car was idling ok tough. The noticeable symptoms were too high engine speed on higher speeds and general "rubbery" feel while accelerating.

After fixing these problems I have very similar consumption readings compared to your current situation (with one liter of added fun in the engine)

I recommend to start by reading the fault codes of engine and transmission, as this is by far the easiest method of troubleshooting.

The codes I got were something like

Torque converter, too much slippage
O2 sensor, bank 2 (something)

Also it was clearly visible in live data that the value of the bank2 O2 sensor remained constant while value of the bank1 O2 sensor varied constantly.

[secretwpn]

Hey, thanks for sharing!
Mine is manual.
Don't have the code reader tho, any recommendations, which one to use or it doesn't matter?

Any fellow clubmates from JKL who can share the reader (beer from my side )?

[HTK12]

I'd start diagnosing by hooking up INPA (it was BMW factory tool when they made e39). Check for codes and check for vacuum leaks with TESTO & can of carb cleaner. While testo is showing the lambda value spray carb cleaner to potential vacuum leak locations. You'll notice even small vacuum leaks by looking at the lambda in TESTO.

Quite a few forum members got INPA & TESTO.

[ppeetu]

Perkele kun ei ymmärrä lontoota juuri yhtään, niin viittiskö joku suomentaa sen ymmärsin että kulutuksista puhutaan, ja omassa 523iA on myös kulutusnoussut, ilman järkveää selitystä.. Kiitoksia jo etukäteen

Is your car manual or automatic?

I had elevated fuel consumption on my 530iA, (10/13/17 l/100km). There was two separate causes for this: the turbine lock of the transmission was not working properly and the primary O2 -sensor of bank2 was faulty.

Car was idling ok tough. The noticeable symptoms were too high engine speed on higher speeds and general "rubbery" feel while accelerating.

After fixing these problems I have very similar consumption readings compared to your current situation (with one liter of added fun in the engine)

I recommend to start by reading the fault codes of engine and transmission, as this is by far the easiest method of troubleshooting.

The codes I got were something like

Torque converter, too much slippage
O2 sensor, bank 2 (something)

Also it was clearly visible in live data that the value of the bank2 O2 sensor remained constant while value of the bank1 O2 sensor varied constantly.

[secretwpn]

Alright, some update: didn't go for INPA yet, but got myself some cheap obd2 scanner and an adapter to round 20-pin bmw diagnostic socket that is under the hood.
Unfortunately it gives me linking error so i can't read the codes with it. And my car does not have obd2 socket inside the cabin, only the round 20 pin.
Do you guys know if INPA will work for me? I'm not that familiar with all those protocols, is it so that inpa will hook up to the same round socket through some adapter and then go to usb port of PC? I wonder will it still work keeping in mine that obd2 didn't.

Thanks!

[HTK12]

Alright, some update: didn't go for INPA yet, but got myself some cheap obd2 scanner and an adapter to round 20-pin bmw diagnostic socket that is under the hood.
Unfortunately it gives me linking error so i can't read the codes with it. And my car does not have obd2 socket inside the cabin, only the round 20 pin.
Do you guys know if INPA will work for me? I'm not that familiar with all those protocols, is it so that inpa will hook up to the same round socket through some adapter and then go to usb port of PC? I wonder will it still work keeping in mine that obd2 didn't.

Thanks!

INPA will, because it was BMW factory tool. Cheap obd2 scanners are quite useless with e39, if you ask me. I read codes from local BMW owners. If it won't work with properly working INPA, you got either a bad module that is jamming the BUS or a wiring issue in the car. I'd start with working INPA and only then check the BUS if you can't communite with the car.

[secretwpn]

Alright, thanks, man! I'll do that!

[HTK12]

Alright, thanks, man! I'll do that!

Forgot to add that you could also a blown fuse, so you might not have power in the diagnotic port. You can find info how to check for power in the diagnostic port by googling something like "bmw 20 pin connector".

[secretwpn]

That's not the case perhaps, cuz the scanner powers up from the port, it just can't link to the car

[HTK12]

As I said it would be easiest to test with INPA. If you can't get INPA yourself, then you could contact a local forum member that got INPA and meet.

[secretwpn]

Alright, an update, just in case it could help someone.

With help of BreeZi BTCF user (whos services i highly recommend btw) we found out that i had a faulty camshaft sensor.

New one from VDO made a 100e hole in my pocket.
Replacing old one was relatively easy job (even though disconnecting the harness from the socket is a bitch, very hard to do with one hand, at least i have struggled good 20 minutes).
Whole job took me about 45 minutes (freezing in the parking lot, if you have a garage it would be faster and easier)

As a result - smoother start, average in-city consumption dropped to ~12l/100km which I'm really happy with.
Highway consumption is at 7l/100km

So, thanks for advises, this question is closed for me for now.