P38 2.5td. Air flow sensor sourcing

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bigwill

bigwill

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anyone recommend a brand or place to find the mass air flow sensor. 2001 model BMW 2.5td. No parts place can get them, Land Rover don't have any, and fleabay have them ranging from £20-£200. Help please
 
bigwill said:
anyone recommend a brand or place to find the mass air flow sensor. 2001 model BMW 2.5td. No parts place can get them, Land Rover don't have any, and fleabay have them ranging from £20-£200. Help please
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What is wrong with it why do you think you need one?
 
bigwill said:
very long story, just eliminating options really.
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Don't look at the MAF then, it does nothing for the running of the engine other than telling the ECU how much exhaust gas is being ingested when EGR is in operation. What is your problem?
 
Mark Piercy said:
Wammers? Your maf tells the ecu air density and temperature??
The egr valve is the last in line then the manifold. Correct?
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The MAF does nothing for the fuelling or running of the engine. It records an airflow, when EGR is active the reduction in flow tells the ECU how much exhaust gas is being ingested. The ECU then modulates the EGR valve to control the exhaust gas ingestion to maintain a combustible air supply just above that which is required, subject to the throttle power demand. To reduce Nox production, by cooling the combustion. The excess air not needed for combustion at the throttle power demand requested is replaced by inert exhaust gas so cooling the combustion and reducing Nox. The MAF was fitted to this engine when EU level 2 emissions with feedback was introduced. The MAF sensor gives the EGR exhaust gas ingestion feedback the regulations demand to give finer EGR control. Nothing more nothing less.
 
bigwill said:
anyone recommend a brand or place to find the mass air flow sensor. 2001 model BMW 2.5td. No parts place can get them, Land Rover don't have any, and fleabay have them ranging from £20-£200. Help please
Click to expand...
I sourced one from Island 4x4 a year or so ago but cannot see them on their web site at present - have you called them?
 
If you buy a good one, ie pierburg or it is Siemens? You get what you pay for.. A friend buys them every two or three years. Cheap ones that is. A clean with up with contact cleaner helps to keep things crisp. But dont touch the bugger physically you can damage it! Also if its got green corrosion on it, its buggered!!
 
On some engines if you unplug it while the motor is running you can hear a drop in engine tone. Sometimes it can be a sign its doing its job!
 
Mark Piercy said:
On some engines if you unplug it while the motor is running you can hear a drop in engine tone.
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Could this be the EGR, not the MAF? That is - the EGR not cutting in due to MAF sensor not 'telling it' to?

There have been quite a few posts on here about EGRs and whether they are any use. I have disconnected and blanked off the wee vacuum pipe to stop dirtying up the air intake, and many people are of the opinion that the engines run better as a result. I am, admittedly, a bit of a tree hugger but I don't believe that EGR is going to save the planet!
I don't mean to hi jack the thread (seems to have gone a bit quiet anyway!) but... as always careful considered views are welcome.
(Along the usual abuse, rudery and **** taking...;))
 
Mark Piercy said:
After 1999 diesel engines started using the maf to influence air fuel mixture??
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Nonsense you read to much Wiki. If the MAF fails on your engine and goes open circuit, it can cause the ECU to become confused because it is not receiving signals it is expecting, but that is as far as it goes. At lease that is what BMW say but what do they know.
 
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Mark Piercy said:
Wammers it was question! Not a statement!
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Ok sorry. But no MAF sensors can't control fuelling on a diesel engines. On later EU emission regs (not your car which is EU 2) they are used to measure air flow relative to throttle demand. But they do not control fuel. Later emissions regs EU 3 for instance, call for much finer EGR control of exhaust gas and combustible air, which is very close to the minimum combustible air needed for the throttle/power demand requested. So if for any particular increased throttle demand the amount of fuel needed to service that would exceed the available air the ECU would not allow that increase until for instance a variable rate turbos charge rate was increased to give the air needed. EU 4 is even tighter and these vehicles will have particle filters fitted to catch the inevitable soot output. But the MAF itself does not control fuelling in a direct sense as it does on a petrol engine.
 
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