Rafi, a good place to start is getting a baseline so you know what you are dealing with. This would be a compression check. Although probably fine, this will let you know if you have small of big issues.

Secondly have the multiplicative (long term) fuel trim read and report the number. If it is high then you have an issue with one or more fuel/emissions components providing the previous doesn't show low compression.

You will also want to pull out at least one plug and look at the end. If it looks black and fouled then you know it is running rich. If it is white then it is running lean. Somewhere in the middle is normal. There are plenty of sites that tell you how to read a sparkplug.

Lastly run a bottle of Techron or Redline fuel system cleaner through. The only 2 additives that i have ever seen actually work. Verified by my video scope!

I was getting 12-13 in the city in D, 8-9 in DS. My long term fuel trim was at 12. Way too high. I replaced my MAF and the mileage immediately went up to about 15.5. I then replaced my pre-cat o2 sensors and the mileage leveled off at about 16.5 city only. After 2 weeks i checked my long term fuel trim and was at 1. Now that is better!

 

Hi guys, any updates on this issue? I just bought 545i last week and I am experiencing the same issue. More than normal fuel consumption but also the throttle is jumping up and down. I am thinking maybe the air flow meter?
Cheers

 

Check the following: 1) Is the air filter clean?, 2) Is there any restriction in the exhaust/catalytic converters (place hand near exhaust - If feels weak use an IR thermometer to check heat levels after the cats. Should be nice and high. If cool, that converter is likely blocked), 3) Do spark plugs if over 50K miles and 4) Check for 02 sensor error codes. Obviously there are more things to consider, but these things should all be checked first.

 

Thanks!

What I did so far:

Day one:

Checked the air filter and it was DIRTY, so cleaned it up and ordered a new one.

Cleaned the sensor from the Air Flow Meter with a Contact spray.

Result - All was the same

Day two:

Put one bottle of STP's injector cleaner on 1/4 of the tank and after running almost empty tank put some 15L of fuel and one bottle of STP's petrol-line cleaner.

Manage to find CRC's Air Flow Meter Cleaner and cleaned the sensor, for the second time.

Result - Idle still ruff but lowered consumption from 13.6 to 9 L per 100 on 136km/h.

Any thoughts?

Cheers

 

I notice that you said you were at 84 kilometers, which converts to about 56,000 miles. I'm pretty sure that your car is wanting new spark plugs...

 

just changed the throttle actuator, consumption now is as it is suppose to be, normal. Total cost around 450 fr.

 

Did changing the throttle body fix your jumping idle?

 

Yes! and at the same time put the consumption in order

Cheers