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Discussion Starter #1
hi all trying to get to the bottom of my maf issues. swapped to a s.h one and still the same

shows as flow too low on planet. the air intake fell off the bottom of the air box but thats back in now

on planet it shows about 500mg on idle. but it says almost the same with it disconnected

my missus has the same air box and maf but heres does not have water pipes to it so cant easily swap them over.

can anyone tell me how to probe multimeter my wifes car maf plug to rule that out. what should i be getting. is there an earth wire on the plug or do i need to use something else?

the car seems to drive alot better since the egr blank even though its stuck at 5%

the car runs fine and boosts ok. its been remapped so i feel its a bit lagging sometimes and im sure its down to the this maf issue

if 500mg is ok why does planet show a flow too low fault
 

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Discussion Starter #4
did a bit of multimeter readings. second pin shows 14.4 volts at idle same as the car so its got supply.

pin 5 has 0.01v if that to ground. reading on the web it should have between 2-4v. does anyone know if this is true. obviousely i did these readings with the car running and the plug off.

the air flow readings seemed exactly the same plugged in or not. i took the car for a run it shows about 500 at idle and 870 at full throttle. so i gather it doesnt work lol
 

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The flow too low code should be for EGR, this is normal as it is blanked.

The reason the reading do not change with MAF disconnected is it is calculating the correct airflow through the sensor.

When you disconnect MAF the ECU calculates/estimates air flow from boost and other sensors and disables EGR and at idle it is very close to real value hence you get the same values.

The low flow code is logged as the MAF records a higher airflow than expected as there is no EGR to make up the air volume, you either ignore the code or have to remap ECU to disable EGR .
 

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Discussion Starter #6
the low flow code was there when the egr was fully working.

my wifes car 2.0 hdi has the egr blanked and doesnt show a fault too low code
 
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+1 - 500mg is normal.

The airflow is higher because normally the EGR would divert a portion of the air into the engine, meaning less air through the MAF. If its blanked then the airflow through the MAF is 'higher than expected' as the EGR should be diverting some of it....

Some cars show a fault with the EGR blanked, maybe newer models, and some cars don't, like my 406.

If you look on Planet on your wife's car, there may be a fault logged but no message on the screen.

Maybe your EGR was partially blocked before blanking it.
 

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I assume the wife's car is a 90 BHP, If so that's why the low flow is not detected due to the different ECU software and mode of turbo control.
 

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Discussion Starter #9
yes it is thanks guys. still cant sort out the lack of ooomph it runs ok but my 1.6hdi mapped was alot quicker anything over 2nd gear in my 2.0hdi 110bhp is pretty naff in comparison

it has no issues getting to speed or going into triple digits just not as agile
 

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Discussion Starter #10
im sure when the egr wasnt blanked it showed the egr opening and closing but the air flow was showing the same as it does now. the egr seems to be stuck at 5 % but it seems to run more consistent now
 

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Discussion Starter #11
thanks all for your advice its nice to learn how these things work

anyway before the egr was blanked the air flow sat at 506 at tickover. it sits at exactly 506 with it disconnected too

does anyone know if the voltage from a siemens system will be similar to a bosch so i can voltage test my wifes car

im sure somethings a miss just cant figure it out. seems odd that the values are exactly the same. ps they were the same with the old maf too
 

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The figure is about right, If you want to be 100% you can calculate the flow that the engine should be pulling.

You can get air temp and boost/atmospheric values from live data and look up air density on google

Based on general data if you use air density base line of 0.85 and boost value of 1.1 bar (eg only .1 over atmospheric as you will get slight boost at idle)

506 gm of air is about 430cc of air times the boost gives about 472cc which is quite close to cylinder capacity (one cylinder at a time is on inlet cycle)

You will not get 100% cylinder filling at low rpm due to valve overlap and low boost allowing air to be push back into inlet tract.
 

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Discussion Starter #13
just find it weird the disconnected maf is so good.

drove the car home its ok and runs fine. 1k to 1.5k is a bit laggy which is why i feel its slower then my 1.6 hdi
 

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Discussion Starter #14
i dont know why but i just realised. when i checked parameters in planet the air tempreture showed 50c

the internal temp works fine and so does the tempreture guage.

is this connected?
 

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Discussion Starter #15
does anyone know how the air tempreture is measured on my car. 2.0 hdi 8v

on the web it says if air temp is high car will not use as much fuel so will be down on performance
 

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There is a thermistor within the MAF which senses the air temp. It is used to calculate air density.

If MAF reports higher temp ECU thinks the air is less dense and therefore it will inject less fuel as ECU will inject the fuel for a lower mass of fuel
 

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Discussion Starter #17
I will check the air temp on my missus car then fit the maf to mine and check again before I purchase a new one I've fixed my laptop screen now
 

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Discussion Starter #19
hi all it seems to get more odd.

checked planet this morning and air tempreture looked ok. at 2c . measured air flow is at 506 i clicked info and this came up



so does that mean as no air is being measured its running in default mode

i plugged my old maf in (which ran worse then the new one)
air flow was very poor but i didnt have it connected to the air box. but planet measured it as 38 and low. so it read it at least

what does every one think. ill be checking my missus car when she gets back
 

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Discussion Starter #20
just to clarify when in parameters it shows 506 at idle and 506 with it disconnected. planet only shows no air flow as a fault.
 
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