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Just happened to drive the girlfriends BMW the other day and noticed it felt like it has lost the low end grunt it used to have also noticed it was only showing 28mpg on the dash. Asked her how long its been like this and she said she hadn't a clue but noticed it was using shed loads of fuel.

Its had a fault scan with a Launch X431 and wasn't showing any faults.

On reading the forums it looked like it could possible be a MAF failure so a brand new bosch MAF was fitted and guess what its still the same.

The vehicle has done 82k and has been serviced regular with genuine parts and quality oil.

At 40mph you have to knock down to accelerate or pull up hills, this vehicle should easy pull up hills at 40mph in 6th.

Anyone any ideas?

There doesn't seem to be excessive black smoke which you would expect if its massively over fuelling.
 

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Discussion Starter · #3 ·
Was the new MAF the same part number? if not then the MAF will need coding to the car
The Bosch numbers are different.

The old unit is - 0 928 400 504
The new unit is - 0 928 400 529

What equipment can code them to the vehicle? also I've never heard of MAFs having to be coded.
 

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The Bosch numbers are different.

The old unit is - 0 928 400 504
The new unit is - 0 928 400 529

What equipment can code them to the vehicle? also I've never heard of MAFs having to be coded.
The diesel MAFs need to be coded if the part number aren't the same as the readings can be slightly different between 2 MAFs.

A good BMW specialist or Main dealer will be able to sort it out for you, they will put there diagnostic scanner on and code it to the DDE(engine ECU)
 

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Discussion Starter · #5 ·
The diesel MAFs need to be coded if the part number aren't the same as the readings can be slightly different between 2 MAFs.

A good BMW specialist or Main dealer will be able to sort it out for you, they will put there diagnostic scanner on and code it to the DDE(engine ECU)
Other than that what else do you think it could be as I'm not 100% sure on the MAF being the problem.

I've just taken the EGR valve off and cleaned it out but it wasn't to bad.

Do they have a problem with the Engine Temp Sensor as this would also cause the vehicle to over fuel.
 

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You could try measuring the resistance of the engine temp sensor but it would be unusual if it was this, I'd expect it to be around 5800 - 600 ohms at 0.c, and 2400-2600 at 20.c

Otherwise view it in live running data on a scanner or laptop with diagnostic equipment.

Also try driving the car for a while with the MAF plug disconnected, if it drives better then it's still a MAF fault(ie coding e.t.c.)
 

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Discussion Starter · #7 ·
You could try measuring the resistance of the engine temp sensor but it would be unusual if it was this, I'd expect it to be around 5800 - 600 ohms at 0.c, and 2400-2600 at 20.c

Otherwise view it in live running data on a scanner or laptop with diagnostic equipment.

Also try driving the car for a while with the MAF plug disconnected, if it drives better then it's still a MAF fault(ie coding e.t.c.)
Going to goto the dealers friday as I've ordered her a new set of rubber mats. I'll try and blag a go with there diagnostics machine. Think I know someone who works there or used to work there.

Worth a try.
 

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Discussion Starter · #8 ·
Ronnie,

Are the cats prone to getting blocked on these 120d engines?? it has done 82k but has been drove hard so I would have thought it would have run clean.

Unless the MAF has been faulty for sometime and its been over fuelling.
 

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Ronnie,

Are the cats prone to getting blocked on these 120d engines?? it has done 82k but has been drove hard so I would have thought it would have run clean.

Unless the MAF has been faulty for sometime and its been over fuelling.
Not as far as I know, you would struggle to get any decent speed if the cat was blocked
 

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Discussion Starter · #10 ·
Not as far as I know, you would struggle to get any decent speed if the cat was blocked
Have just ordered a BMW Dealer level GT1 DIS / SSS Diagnostics tool so should be able to pin point what it going on with the vehicle. Also should be able to match the new MAF up with this tool.

If the cat was partially blocked it could cause this fault but it could be a long shot as the missus drives quite hard so would expect it to run clean ish. the EGR Valve was fairly clean.

Also removed the map sensor and cleaned this off, but again it wasn't to bad.

Vehicle just feels flat below 2000revs. Going to also check all the hoses to make sure nothing has split.

Is there any hose to look out for?

Also Ronnie, cheers for the help and input and to wish you all the best for 2009
 

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Have just ordered a BMW Dealer level GT1 DIS / SSS Diagnostics tool so should be able to pin point what it going on with the vehicle. Also should be able to match the new MAF up with this tool.

If the cat was partially blocked it could cause this fault but it could be a long shot as the missus drives quite hard so would expect it to run clean ish. the EGR Valve was fairly clean.

Also removed the map sensor and cleaned this off, but again it wasn't to bad.

Vehicle just feels flat below 2000revs. Going to also check all the hoses to make sure nothing has split.

Is there any hose to look out for?

Also Ronnie, cheers for the help and input and to wish you all the best for 2009
How much that cost you? they are usually big money :eek.......:confused also usually only available to main dealers
 

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Discussion Starter · #12 ·
How much that cost you? they are usually big money :eek.......:confused also usually only available to main dealers
Yep the Visa got a good bashing buying it. Think I was still drunk this morning when I ordered it. :silly

It'll end up getting used anyway as I do quite a bit of work in the garage and for other garages in the area.

I have a Launch X431 but it isn't that good on BMW vehicles.

You know of any hoses that split on these engines or vacuum hoses?
 

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Just happened to drive the girlfriends BMW the other day and noticed it felt like it has lost the low end grunt it used to have also noticed it was only showing 28mpg on the dash. Asked her how long its been like this and she said she hadn't a clue but noticed it was using shed loads of fuel.



At 40mph you have to knock down to accelerate or pull up hills, this vehicle should easy pull up hills at 40mph in 6th.




Do yah think?

My 120d only shows 30mpg in gentle use around town!

Also, I would have to change down to accelerate from 40 in 6th - infact I dont even use 6th unless Im doing more than 55mph, otherwise its useless!

Sounds like your car is normal in my opinion - either that or mine is also fooked!!

(2007 120d M Sport 20K).

Andy
 

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Discussion Starter · #16 ·
Do yah think?

My 120d only shows 30mpg in gentle use around town!

Also, I would have to change down to accelerate from 40 in 6th - infact I dont even use 6th unless Im doing more than 55mph, otherwise its useless!

Sounds like your car is normal in my opinion - either that or mine is also fooked!!

(2007 120d M Sport 20K).

Andy
Really should do more than 30mpg around town.... I really struggle to get 30mpg on a good run never mind around town....

Next week I should know more when the BMW GT1 Diagnostics machine lands....
 

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Discussion Starter · #17 ·
Was the new MAF the same part number? if not then the MAF will need coding to the car
Ronnie,

Just been the dealers to pick some parts up and talked to the tech guy. I asked about getting the new MAF coded and he said he had never heard of that. Also he couldn't give me any other answers as well.

Gotta wait till my GT1 lands now to try and track the problem down.

Maybe a sticking injector? She does always use supermarket fuel...
 

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Ronnie,

Just been the dealers to pick some parts up and talked to the tech guy. I asked about getting the new MAF coded and he said he had never heard of that. Also he couldn't give me any other answers as well.

Gotta wait till my GT1 lands now to try and track the problem down.

Maybe a sticking injector? She does always use supermarket fuel...
That's dodgy :lol

Tell him to listen in class http://www.air-mass-meter.com/2008/bmw/0-928-400-527-or-0-928-400-314-–-re-programming-needed/
 

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Discussion Starter · #19 ·
Did get the impression he didn't have a clue what he was talking about. :confused

But just reading the link it looks like its the older BMW's that suffered but maybe they have updated the 120d MAF with the new part number I got. Going to give it a update next week anyway when the GT1 lands.

Tested all the vacuum lines today and all boost hoses. Nothing wrong with any.

Also did some datalogging with the Launch X431 (It's basic on BMWs) the requested & actual boost and also rail pressure are good.
 

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Thought i'd butt in about now.

If car is flat as fook try unplugging the EGR solenoid (next to alternator)

If car is better your EGR calibration needs sorting. Will cost you about £90 and only folks with GT1 can do it.

Unless MAF fixes it. I'm sure Ronnie will back me up here - don't get lost in trying different sensors etc unless you've had a proper dealer scan.

All other systems apart from GT1 will not give the full picture of all the car's inputs and outputs.

I wasted £400+ changing all kinds and 3 none dealer scans - I have a good selection of spare sensors should you need one !!
 
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