Changed MAF but acting strange (BMW 320TD)

12th February 2014, 16:55

Had my MAF changed today as it came up as faulty on a diagnostics test. But when I'm accelerating it makes a weird whistling noise and there is still a flat spot.

Anyone have any idea what's going on? Maybe because It's a new part it needs time to adjust or something.

12th February 2014, 18:42

swirl flaps :O

12th February 2014, 20:03

Already blanked them

12th February 2014, 20:33

cleaned the egr?

12th February 2014, 20:46

Quote:

Originally Posted by vtr91

cleaned the egr?

Yep! Apparently the ecu needs time to adjust to the new MAF but that still doesn't explain the whistling.

12th February 2014, 20:48

Whistling is a sign of turbo problems according to google, get it checked out as could be expensive if you leave it.

12th February 2014, 20:50

Thats aload of rubbish.
Ecu will read what the airflow meter is registering straight away.
You checked the sensor outputs and live readings?

Sent from my GT-I9300 using Tapatalk

12th February 2014, 21:11

Cant see the turbo suddenly breaking as soon as I get back in the car after getting the MAF done!

12th February 2014, 21:23

Are you aware that the mass air flow sensor (which I presume that's what you mean by MAF) isn't anything to do with the fueling and running of a Diesel engine.
It's used purely to monitor how the egr is working
I think the best places to look would be egr fiction and charge air system for leaks. Oil residue should be a sign of of a charge air leak.
Do you know if there are any fault codes in it? Has the original fault code gone?

12th February 2014, 21:30

Quote:

Originally Posted by Beaniemoo

Are you aware that the mass air flow sensor (which I presume that's what you mean by MAF) isn't anything to do with the fueling and running of a Diesel engine.
It's used purely to monitor how the egr is working
I think the best places to look would be egr fiction and charge air system for leaks. Oil residue should be a sign of of a charge air leak.
Do you know if there are any fault codes in it? Has the original fault code gone?

Yes I am aware. I think the mechanic has obviously not put something back on properly as it sounds like there is a leak, air being sucked in but escaping hence the whistling strange sound. The eml is still on so there may still be codes on there.

12th February 2014, 22:31

Quote:

Originally Posted by Beaniemoo

Are you aware that the mass air flow sensor (which I presume that's what you mean by MAF) isn't anything to do with the fueling and running of a Diesel engine.
It's used purely to monitor how the egr is working
I think the best places to look would be egr fiction and charge air system for leaks. Oil residue should be a sign of of a charge air leak.
Do you know if there are any fault codes in it? Has the original fault code gone?

This is the biggest load of shite ive read for a long time!
I take it you have never driven a diesel car with a faulty MAF sensor?
Flat as a turd.
A MAF sensor is not to monitor how the EGR is working at all!
MAF sensor measures ambient incoming airflow so it can fuel accordingly.
From this i bet you dont know how the EGR works or what it even does.

12th February 2014, 22:33

and reference the whistling, you probably have a boost leak.

12th February 2014, 22:37

Quote:

Originally Posted by vtr91

and reference the whistling, you probably have a boost leak.

Thanks mate! I was thinking the egr is on the total opposite side of the engine to the airflow meter. Do you think the mechanic didn't put something back on properly? Also it's still flat but it's like flat spot rather than being flat all the time.

12th February 2014, 22:44

The EGR will cause that symptom if its coked up.
Done 2 at work this week, one on a vauxhall and one on an alfa romeo.
Both the same symptoms (pretty sure they were the same engines too) it was pretty flat until the turbo started spooling up then you was off.

It wasnt very driveable/pretty flat until the turbo started spooling.

Check all your boost hoses first, make sure none are split or come unclipped. If you have a boost leak, it will give you flat spots or little boost, depending on whats going on.

Im sure he will have put it back together properly. IIRC the MAF sensor is inside of the airfilter housing with 3 screws?

12th February 2014, 22:50

Biggest load of shit you've read in a long time!? Please don't be rude.
Sorry I really don't want to start an argument on this but the air mass on a diesel isn't to do with fueling as there is no regulation of the air on a diesel except for dpf burn off.
The reason a diesel would be slow without an air mass plugged in is because it can't monitor egr rates.
I have worked for Mercedes for 14 year and am a master technician so have decent experience of diesel vehicles.

This link to also confirms this

http://www.vdo.com/generator/www/com...sensor_en.html

I can also explain how it works out if the egr is working too if you like?

12th February 2014, 22:57

FML!

I give up.

12th February 2014, 23:09

Quote:

Originally Posted by vtr91

The EGR will cause that symptom if its coked up.
Done 2 at work this week, one on a vauxhall and one on an alfa romeo.
Both the same symptoms (pretty sure they were the same engines too) it was pretty flat until the turbo started spooling up then you was off.

It wasnt very driveable/pretty flat until the turbo started spooling.

Check all your boost hoses first, make sure none are split or come unclipped. If you have a boost leak, it will give you flat spots or little boost, depending on whats going on.

Im sure he will have put it back together properly. IIRC the MAF sensor is inside of the airfilter housing with 3 screws?

I cleaned the egr on Sunday. Was so clogged up, didn't fix the problem so had the diagnostics done, said airflow meter out of range so got a new one and as soon as I left the mechanic I noticed the weird whistling noise. The new MAF must be doing something as said the flat spot is from about 2k revs then it powers out of it. But something still isn't right.

14th February 2014, 05:20

You've got a leak somewhere. Open the bonnet and try to locate the whistle by ear, I'd look at the pipes first. Sometimes when you move stuff around you break something else, might be a cracked seal or perished pipe. How old is your bmw?

14th February 2014, 15:35

Quote:

Originally Posted by Manu

You've got a leak somewhere. Open the bonnet and try to locate the whistle by ear, I'd look at the pipes first. Sometimes when you move stuff around you break something else, might be a cracked seal or perished pipe. How old is your bmw?

Turned out when the mechanic changed the MAF the turbo gasket split due to it being deteriorated so all fixed now!

14th February 2014, 15:54

ah there you go. I lost count of how many times you fix something, and in the process of fixing it you have to move other bits, which break because they're too old and get brittle over time. I had to change quite a few bits and bobs recently, pita