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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30174
Location: Hertfordshire and Hampshire


PostPosted: Fri Dec 28, 2012 10:18 am    Post subject: Cleaning or replacing your MAF Reply with quote

General road use (traffic film) and more likely excess oil from sports panel filters (like K&N etc) will contaminate the MAF (Air Mass Flow Sensor) and hence confuse the DME about how much air is getting into the engine and therefore the correct amount of fuel to inject.



Always wick new or newly oiled filters in kitchen paper or newspaper (tightly wrapped) for 24 hours or over night to remove excess oiling.

MAF contamination usually makes the car feel strangled (but can lead to extreme fuelling issues resulting in stalling).

If disconnecting the MAF (and hence forcing DME to use default air-fuel ratio at idle) results in smooth running, that indicates the MAF is at fault.

(can be worth cleaning out the throttle-body too)

MAFs also just get old (or the contamination is burnt on and can't be removed) thus requiring a new MAF - it is ultimately a wear and tear item.

Wash your MAF with IPA (isopropyl alcohol) if contaminated.


IPA MAF wash.

Cleaning or replacement of a MAF takes about 30 secs.

Clean costs the few quid for a can of IPA, replace cost are circa £180 (I guess at the worst you may have to buy a T20 Security Torx screwdriver from Halfords if you don't already have one or can't borrow one).



MAF:

Remove T20 Security Torx screws here:



Wash with this (do a google search, or places like Maplin and other electronics shops sell it for component or tape-head cleaning etc).



IPA (isopropyl alcohol, not the beer) evaporates and leaves no residue.

Spray IPA into MAF, gently shake excess IPA and suspended dirt from hot wire cavity.

Repeat until no further debris in MAF (only two or thee times).

The reason: although the IPA evaporates completely, if dirt is not "flicked" out whilst IPA is still liquid it will simply be re-deposited on IPA evaporation.

PICTURE IS FOR ILLUSTRATION ONLY - DO NOT REMOVE THE COVER.
SIMPLY GENTLY SPRAY INTO MAF ENTRY/EXIT HOLES



DO NOT INSERT ANYTHING INTO THE APERTURES!

If you break the hot-wire (film), you buy a new MAF.

List of suppliers here:
http://www.911uk.com/viewtopic.php?t=61508

Best Bosch prices are circa £160-180 (don't bother with cheap Chinese copies).
 
  
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cheshire911
Estoril


Joined: 10 Jun 2012
Posts: 3852



PostPosted: Fri Dec 28, 2012 6:28 pm    Post subject: Reply with quote

I find your threads very helpful and they help to grow my understanding of these lovely cars. I used to tinker a lot with motorbikes (classic british bikes in the 70's) and less so with cars - had a Hillman Minx and then an MGB Roadster - had to maintain them myself as I was a student. Now I don't tinker with any cars and don't have bikes - but my curiosity to understand them grows and I can hold a meaningful discussion with a specialist about what he reckons my car needs doing and why and the options available. I find your posts very informative and appreciate your willingness to help fellow Porsche owners. Thanks.
_________________
996 2002 X50 Turbo Manual
"Once bitten; forever smitten"
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30174
Location: Hertfordshire and Hampshire


PostPosted: Fri Dec 28, 2012 7:42 pm    Post subject: Reply with quote

Salut
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30174
Location: Hertfordshire and Hampshire


PostPosted: Sat Apr 27, 2013 11:40 pm    Post subject: Reply with quote

I should have included some basic elimination diagnosis (this FAQ was written from the point of view you knew your MAF was dodgy):

Disconnect the MAF and see what effect it has.

If the idle returns to normal, then it is the MAF.


Dirty MAFs can also result in misfiring at low rpm and flat spots in the rev range.
 
  
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GT4
Nordschleife
Nordschleife


Joined: 08 Nov 2008
Posts: 30174
Location: Hertfordshire and Hampshire


PostPosted: Thu Feb 18, 2016 11:42 pm    Post subject: Reply with quote

eBay.de still has genuine Bosch MAFs @ £120 (plus postage)

http://type911shop.co.uk shows @ £170
 
  
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