mbrokof

Active Member
Hello All,

I read somewhere I think on here that the IAT determines the fuel amount, meaning if the MAF is being unplugged it goes into some kind of emergency mode and uses -40 degrees C for fuel. Hope that's correct.

Is this the only bit in the MAF that determines the fuel or is it also determined by the input signal? If measured through from the MAF plug to the ECM which value should I get?

KR
Matthias
 
Thanks @hd3, how do you recognize it that it's on -40? Via a scanner? Maybe never have paid attention to it.
Re the other that might be down to trial and error.
 
how do you recognize it that it's on -40? Via a scanner?
yes .. via my 'hawkeye-total' device.
.............
i've got a maf issue that needs sorting .. i've yet to investigate why
a new bosch maf didn't fix it. ..
if there's no leak between maf and turbo inlet ..[yet to look]
then my engine remap procedure .. might be the culprit
[ cause i left the ronbox connected at the time
[ plus there might have been a pierburg maf fitted at the time ..
am currently in mafless mode .
[ runs great .. but didn't pass emissions at mot time ]
i'd like to see what might happen if just the iat sensor be connected.
but haven't figured the wiring out .. yet.

cause in the meantime .. the alternator packed up.
and battery also needs replacing.
hippo's been parked up fer 7 weeks ..
only just got dosh-fund to deal with that yesterday.
'n alt.+bat. a priority ;-]

'n my computer broke .. boot-drive failed ..
has taken 2 weeks to sort out apps n files n licenses etc etc etc
... and i lost some maf wiring diagrams i'd saved ;-[

.
 
@hd3 Sorry to hear/read that it's not going well at the moment. Could have sent a re-emf charger to test on the battery, but still lacking some parts that I need.

I have no Hawkeye, but a pscan, maybe must have a look if I can find it. As far as I remember I haven't seen it.

With the wiring I might be able to help you. Lately I had a good time finding something in the manuals:
C0149
upload_2023-4-18_20-41-47.png

No. 1) IAT
No. 2) That one goes via a knot to some other parts so might be good to keep it, I guess
No. 3) earth MAF
No. 4) Output MAF
no. 5) Input MAF
Do you want to unplug it on the MAF side or on the other side and take out all wires except for the IAT? I had a look on the MAF plug, but no idea how to get it open, so thought the other side might be easier.

Re Crash, I have only Windows on boot drive, the programs I have moved on other drives. Last year or the year before I moved also the documents, pictures etc. to a NAS. Didn't have much problems with hard drive/s so far, but Windows crashes which always cost me time to find the programs that were installed again.
 
With the wiring I might be able to help you
cheers :)
i'll note n save the details.

Do you want to unplug it on the MAF side or on the other side and take out all wires except for the IAT?
no idea yet ..
if experimenting via the maf unit .. would mean sacrificing a maf sensor probably..
unless there's a way to temporarily isolate certain pins ..
as is .. i've got a cut-down dummy maf fitted .. [ i cut off the section that's in the airflow ]
keeps the cable plug protected.
now .. it's .. fit-workin-maf-4-mot .. replace with dummy maf when out of sight of mot garage ..
[ cause the current fault is ''low maf signal'' ..
[ be ok-ish on the flat .. but a p.i.t.a. uphill ...
[ and .. the only way home is via rather steep climbs

i just want to find out if it'd pass mot emissions .. with just the i.a.t. wired up.

certainly drives well without the maf connected,
no smokey exhaust .. mpg dropped by '2' ..

i'll probably attack the maf fault issue after this mot .. which is soon-ish ..
as i need to inspect the maf > turbo ducting 1st ..
n that means undertray 'off' by the looks of it ..

Re Crash, I have only Windows on boot drive, the programs I have moved on other drives.
main issue were getting a suitable OS for this machine .. it's a 2012 mac ..
and apple don't like to supply older OS versions .. well .. they don't make it easy ..
they'd rather you buy a new computer.

....................................................................................................................................
re. MAF issues.
just a side-note to readers who have a ron-box + pierburg maf fitted :
should you Need to disconnect the maf, remove the ron-box altogether .. as well .
if not .. it'll drive like shyte ..:cool:
.
 
cheers :)
i'll note n save the details.
You're welcome:)

no idea yet ..
if experimenting via the maf unit .. would mean sacrificing a maf sensor probably..
unless there's a way to temporarily isolate certain pins ..
as is .. i've got a cut-down dummy maf fitted .. [ i cut off the section that's in the airflow ]
keeps the cable plug protected.
now .. it's .. fit-workin-maf-4-mot .. replace with dummy maf when out of sight of mot garage ..
[ cause the current fault is ''low maf signal'' ..
[ be ok-ish on the flat .. but a p.i.t.a. uphill ...
[ and .. the only way home is via rather steep climbs
I have sacrificed an old one which I tried to cut open in the beginning with a Dremel like tool, but got to nowhere so far. It seems completely poured into plastic. Didn't follow up further.
You can separate the pins in the 'black box' except for the number two on the MAF side. At least I couldn't locate that one. I'd
really like to know on mine if it's on -40 degrees then. In the live data section it is not, when completely unplugged, checked it today, Maybe I should check all the other bits in Pscan if it's there, before I start going into un-connecting single pins.
-Having the same issues when I plug it in uphill poor flat quite ok, West London so not an issue except for some minor uphills but even those are annoying. Proper hills is really bad.
- Maybe I would have a low maf signal as well if using Hawkeye. When I saw Andyfreelandy's overview once from Pscan I thought that should/could be a reference, but never got close to there unless unplugged.
- read somewhere yesterday or the day before that they took off the grille from the MAF, but shall not be that good and put it back in. You took off the whole bit then?

i just want to find out if it'd pass mot emissions .. with just the i.a.t. wired up.
certainly drives well without the maf connected,
no smokey exhaust .. mpg dropped by '2' ..
i'll probably attack the maf fault issue after this mot .. which is soon-ish ..
as i need to inspect the maf > turbo ducting 1st ..
n that means undertray 'off' by the looks of it ..
- I think that would be interesting if it passes with a dummy. I think I mentioned a while back that mine had passed the MOT with the MAF unplugged, really bad, but it did. I guess the emission stick somehow works. Went there a second time saying sorry was unplugged (was prepared to pay them 20 quid or so, but they said no is ok) the mechanic was really happy saying values almost like new. Would be nice to know with pin pulled for input what the values are, but can't go there again. If input missing there still should be a fault code, but if output unplugged if that happens as well? Maybe I will try that one as well, just no output, but input and IAT. My mpg went down as well, not that much I think but good enough. Also wondering about possible side effects on missing input signal now that you mentioned it. Maybe I also should send an email to buyer of the stick. He once mentioned in a call that he got a tuning box on his A6 and told the manufacturer to change values to his calculations. Am wondering if those were related to MAF.
- Had also no smoke, when cold smelt bad, but once a bit warmer couldn't smell anything anymore. When cold that might be that I still haven't changed the glow plugs as I am reluctant to break one off, but also never drove it really hot before trying.

Never had an Apple computer and considering how bad the iPhone became since Jobs is gone,...
 
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I have unplugged the input. It drives better similar to complete unplugged I'd say, but I am not sure if it uses -40 as well as the fuel con is bad at the moment. Have started a thread on pscan.eu forum but no response on how to find the temperature yet. Might need to find a Hawkeye if not working.
 
I have unplugged the input. It drives better similar to complete unplugged I'd say, but I am not sure if it uses -40 as well as the fuel con is bad at the moment. Have started a thread on pscan.eu forum but no response on how to find the temperature yet. Might need to find a Hawkeye if not working.
The MAF is combined with the intake temperature sensor, so unplugging it results in no MAF reading, or intake air temperature. The -40°C is a standard OBD2 reading when there's no signal available, but from memory the ECM defaults to a 20°C intake temperature as a reference for timing calculations.
 
Hello Nodge,

Sorry to hijack this.

My MAF is unplugged at the moment and I get -40C for temp but the MAF reading is still there.

Fluctuates in the 400-500+ range - is this normal? Should it be a N/A or a solid/emergency figure?

I have a code for both MAF and IAT but the scanner sees a value and it would appear to be dynamic - changes with revs etc.

Could it be - and I am clutching at straws here - could it be that my car is re-mapped and that is why I am getting the rich exhaust smell and the car is sluggish down low when MAF plugged in and dangerously quick with the MAF unplugged? DANGEROUSLY quick.
 
with the maf unplugged .. the ecu will read a default maf-map.
probably referring to other fluctuating values ..
like air temp / rpm / map [turbo-boost]
maybe what your seeing are the values calculated via the ecus' default maf-map.

that's a guess :cool:

DANGEROUSLY quick
td4 ? ..
title-card.jpg

well ok :) .. go-pedal response with maf unplugged will be a lot quicker ..
and def. feel faster by comparison to a failing maf.
remapped ? .. that's possible .. the stage1 will take it to aprox. 140bhp.
i guess you could contact prev. owner to find out.
what's the mpg been since you owned it ?

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