MAF sensor unplugged

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sweeney

New Member
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So, further to my earlier thread where my wife has had a couple of problems with the Disco being a bit juddery especially at low revs, I cannot seem to replicate the problem now so I think maybe just a bit of muck picked up in the fuel tank.
However, seeing as there seems to be a lot of threads on how the MAF can be a pain I took it for a quick spin after unplugging it. What should it feel like when I have done this? I'm not sure there was a great deal of difference, still felt smooth on acceleration, maybe revved slightly higher before changing gear but not loads. Any ideas what difference if any it should make?
Cheers.
 
sweeney said:
So, further to my earlier thread where my wife has had a couple of problems with the Disco being a bit juddery especially at low revs, I cannot seem to replicate the problem now so I think maybe just a bit of muck picked up in the fuel tank.
However, seeing as there seems to be a lot of threads on how the MAF can be a pain I took it for a quick spin after unplugging it. What should it feel like when I have done this? I'm not sure there was a great deal of difference, still felt smooth on acceleration, maybe revved slightly higher before changing gear but not loads. Any ideas what difference if any it should make?
Cheers.
Click to expand...


good point-strange it made no difference?
Assumptions would indicate that its faulty/inoperative if it still runs as normal???
since the thread ref "it should be a servicable item" (?!) ive been thinking of doin the same with mine as my disco is sluggish...

hope someone has the answer!
 
have had mine unplugged for about a year now mainly cos i thought my td5 very sluggish....it certainly got rid of sluggishness...more reactive...only downside i found was when shes started tends to try and "die" for first 10 yards then goes fine...something to do with the ecu i think. seems to get rid of the "turbo lag"
 
foss said:
unlpugged mine last night & it started & drove as normal-another land rover part worth having!:D
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Recently replaced my MAF after being told/shown on diagonstics it should read 60% or summat like that and that it was actually reading zero!
After buying/putting a new one on, WOW....no difference at all! Still runs as well as it did the day I got it, MAF or no MAF.
 
Interesting comments. Nanocom told me that there was a problem with air flow so I replaced the MAF. FOUR MONTHS LATER, same bloody problem. I think I'll disconnect it in the morning and go for a spin.
 
danam1 said:
So are you saying the MAF is not needed if the EGR has been removed?
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Best to keep it plugged in if it's working. A circuit missing may sometimes effect the ECU. When EGR is operating the reduction in air flow through the MAF indicates how much exhaust gas is being ingested. The ECU uses this info to modulate and control the amount of EGR applied subject to power requirement Etc.
 
Hi Sierrafery,

Maybe it is time for you to put Your knowledge into a how to regarding MAF falure, also reference EGR etc.

Cheers
 
I'm speaking about how the engine MANAGEMENT works cos the MAF is part of that not part of the engine... about how a complicated electronic system calculates the amount of fuel which gets into the combustion chamber based on several sensor's inputs not how a Hornsby-Akroyd engine is running:cool:

the main question is still obsessive: WHY DID THEY FIT A MAF SENSOR ON ENGINES WITH NO EGR FROM FACTORY?
 
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Untill i'll learn more about how a diesel engine works here is some official data about what the MAF signal is used for in some modern engine MANAGEMENT:
http://www.vaglinks.com/vaglinks_com/Docs/SSP/VWUSA.COM_SSP_358_Hot_film_Air_Mass_Meter.pdf , to be easyer for those without much patience you'll find at
1. page 8 at the top :
"The hot-film air-mass meter HFM 6 is used to measure the intake air mass. The engine control unit calculates the exact intake air mass from its signal.....
With diesel engines, the signals are used to control:
- the exhaust gas recirculation quantity and
- the injection time."
2. page 14 at the bottom:
"Signal use
Diesel engine
The measured values are required by the engine control unit to calculate the exhaust gas recirculation quantity and the injection quantity."

The described sensor works exactly like the one used for Td5s too.
 
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sierrafery said:
Untill i'll learn more about how a diesel engine works here is some official data about what the MAF signal is used for in some modern engine MANAGEMENT:
http://www.vaglinks.com/vaglinks_com/Docs/SSP/VWUSA.COM_SSP_358_Hot_film_Air_Mass_Meter.pdf , to be easyer for those without much patience you'll find at
1. page 8 at the top :
"The hot-film air-mass meter HFM 6 is used to measure the intake air mass. The engine control unit calculates the exact intake air mass from its signal.....
With diesel engines, the signals are used to control:
- the exhaust gas recirculation quantity and
- the injection time."
2. page 14 at the bottom:
"Signal use
Diesel engine
The measured values are required by the engine control unit to calculate the exhaust gas recirculation quantity and the injection quantity."

The described sensor is exactly the same with the one used for Td5s too.
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That'll save on spares then, the MAP sensor can be removed and thrown away. Diesels are throttled by fuel not by air, the only thing the ECU would take notice of from the MAF is along with information from the fuel temp sensor and MAP sensor and throttle demand for fuelling is the inlet air temperature. For any particular throttle demand power setting fuel is increased to attain that request, airflow through the MAF has nothing to do with it. For any given throttle request, engine speed, manifold pressure there is always the same volume of air in the combustion chamber. When EGR is operating that volume will contain less oxygenated air but fuelling for for throttle RPM demand manifold pressure does not change. If it did the engine would slow down and lose power. The only thing that is changed to throttle the engine is fuel quantity. Think you need to define modern, the TD5 was developed in the 1990s to meet the then up coming EU III emission regulations. It is hardly a modern engine. Discontinued in 2007 because it could not meet EU IIII regs. More modern engines use a much finer EGR ratio, when EGR is active where the burnable air is reduced to just above the absolute minimum required for combustion at any particular RPM request manifold pressure to reduce Nox production, this can cause soot particles to form due to the cooler combustion, that is why with more modern EGR systems a particle filter is added to the exhaust system to capture any particles caused by EGR operation at lower engine speeds. These soot particles are then burned off at higher speeds and exhaust gas temps, Eg on the motorway. Using a modern EGR engine constantly around towns and cities with low engine RPMs at low road speeds will eventually block the particle filter causing running problems. The engine must be run at higher engine speed exhaust temps now and again to purge the filter.
 
sierrafery said:
I'm not gonna contradict you out of respect, if you have patience or you are bored and want some entertainement read this whole thread http://www.aulro.com/afvb/discovery-2/201719-how-completely-get-rid-maf-de-egrd-td5.html to see how hard i sustained the ideea that the MAF on a Td5 is there only for EGR ... too bad that you wasnt there then :cool:
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You read things but do not understand. The basics of diesel operation are very simple. Until you do understand stop talking rubbish. The reasons for not removing MAF sensors from the circuits has been mentioned many times. On newer EGR set ups if anything is disconnected the ECU shuts down. But the MAF does NOT control fuelling subject to air flow on diesel engines. Harry Potter books are good, but there really are no Wizards.
 
I'm not talking about the diesel engine but about it's EEPROM based electronic management with adaptive strategy, and even if you think i dont understand how the diesel engine works i understand well how electronics are involved... my "experiment" was not about leaving open circuit on the MAF signal but substituting it with something else to make the ECU ''think" it's there and not go to default and my based exactly on what you are strongly sustaining that it's signal is only for EGR , so as long as the ECU gets a closely similar signal the engine should not be affected at all cos as you said it's "throttled by fuel"... the engine will run on the amount of diesel which is managed by the ECU and as long as the ECU is using the MAF signal for injector management too the amount of fuel injected is altered by it's signal

It seems to me that you insist to compare a mechanically throttled diesel engine with an electronically managed one and contradict all the official statements that the MAF is used for injection management too ... cos IMO that's what we are talking about... but what can i do if i dont understand, as long as i respect the forum's rules and not being rude i'm just excercising my universal right of free speach, that's why i have that purple signature as well:cool:
 
sierrafery said:
I'm not talking about the diesel engine but about it's EEPROM based electronic management with adaptive strategy, and even if you think i dont understand how the diesel engine works i understand well how electronics are involved... my "experiment" was not about leaving open circuit on the MAF signal but substituting it with something else to make the ECU ''think" it's there and not go to default and my based exactly on what you are strongly sustaining that it's signal is only for EGR , so as long as the ECU gets a closely similar signal the engine should not be affected at all cos as you said it's "throttled by fuel"... the engine will run on the amount of diesel which is managed by the ECU and as long as the ECU is using the MAF signal for injector management too the amount of fuel injected is altered by it's signal

It seems to me that you insist to compare a mechanically throttled diesel engine with an electronically managed one and contradict all the official statements that the MAF is used for injection management too ... cos IMO that's what we are talking about... but what can i do if i dont understand, as long as i respect the forum's rules and not being rude i'm just excercising my universal right of free speach, that's why i have that purple signature as well:cool:
Click to expand...

No they are all the same, they are throttled by fuel NOT by air, so what is going in through the MAF other than it's temperature is totally irrelevant to fuelling. Diesel engines are not throttled by air but by fuel something you seem unable to grasp. For any given engine RPM, manifold pressure there is ALWAYS the same amount of compressible gas in the cylinder. That maybe pure air or a combination of air/exhaust gas when EGR is operating. It never changes it is always the same. To make a diesel engine rev higher you give it more fuel to slow it down you reduce fuel. Same applies to any diesel engine. They are very simple things to understand.
 
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