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Discussion Starter #1 (Edited)
Hi all e46 fanatics.
2002 320i facelift M-Pack2, M54B22 Engine, Orient Blue, Japan import. 64,000km on it. Just bought it and I just love this car especially the handling is outstanding.

But it suffers from excessive fuel consumption 16-19L/100km it's 15-18 MPG (driving like miss daisy), this is just unbearable even in clogged city stop and go.
Fuel used: Regular(93 octane) mostly, sometimes Premium(95 octane).
Engine has slight vibration on cold startup, but normalizes quickly.
The car feels like it lacks power.
Other than that the car feels normal, couldn't find any symptoms. No idle problems no stalling no whistling while revving. No check engine light.

Checked with PA Soft BMW scanner after clearing all errors and it returned these codes:

5A/12 - Exhaust temperature before catalyst, bank 1, signal line, short circuit to negative
5B/12 - Exhaust temperature before catalyst, bank 2, signal line, short circuit to negative
5D/12 - Exhaust temperature after catalyst, bank 2, signal line, short circuit to negative
3F/14 - Control unit self-test 3
85/08 - Signal, CAN ASC 3, timeout elapsed
34/02 - Solenoid valve, exhaust flap, short circuit to negative or open circuit

I've checked Engine Electronics Fuse Pack in underhood E-Box, all 5 fuses are ok. 4th fuse is for Oxygen sensors and oxygen sensor heater circuits(Lambda sensors).
Checked Coolant/Engine temperature using hidden OBC menu, driving after cold start after ~7mins temp is 90-92C, outside temp 33C. So the thermostat seems good, haven't checked how it holds temp on highway though.
Unplugged MAF when engine running, idle RPM dropped a little and quickly normalized, plugged it back in and engine stalls. Is this normal?
Drove a little with MAF unplugged and throttle felt more responsive, but fuel consumption rose.
Could it be a vacuum leak? haven't checked, but then again even if there is a vacuum leak it can't be the reason for such an excessive fuel consumption.
I'm suspecting Lambda O2 Sensors, but some people say that those errors in shadow memory are common and should be ignored, is it true?
Gonna check Lambda O2 Sensors with multi-meter tomorrow and see.

Any suggestions are welcome

P.S. does INPA work on BMW Scanner hardware?
 

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Use the On Board Computer to track Average Miles/Kilometers per Hour. Reset this for every fuel fill up along with the Average Miles/Kilometer per Gallon/Liter.

If the Average Miles/Kilometers per Hour is less than 20 MPH/32 kph, the this is the source of your 15-18 MPG, as you mentioned clogged city stop and go traffic.

For every minute your engine is idling at a stop, you achieve exactly 0 MPG/kpl.

Unless you constantly turn your engine off at stops and then restart it, do not expect anything better than 18 MPG in city traffic.

Also make sure your exhaust/muffler flap is open when the engine is not running. Look inside the tail pipe with a flash light/torch and make sure the butterfly valve is open when the engine is not running.
 

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Discussion Starter #3 (Edited)
my car doesn't have exhaust/muffler flap, Japanese versions don't have it as far as i know.
What I did after my post:
I discovered that DISA was stuck in open position, I removed it moved the flap around a bit with hand and it started working, it passed the finger on hole 45° test so i've put it back on. It's still working fine.
Then I was doing some testing with INPA and i was getting negative fuel trims and finally I figured I should change fuel filter, FPR was dead and all the fuel was going to engine instead of return line. Fuel trims went back to normal, I think close to ideal? see screenshot below
But the consumption still stays very high
I've asked about 10 owners of the 320i facelift e46s in my city (most of them also imported from japan) about consumption and to show me their OBC readings which ranged from 11.2L to 13.1L/100km, they said they're getting 7-8L/100km on highway, so i've reset consumption OBC and hit the highway drove about 90km average speed 100km/h and consumption showed 11.3L/100km, that's way too much for highway

I'll post INPA screenshots of before and after fuel filter change with dates, all taken when engine at operating temperature.




 

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