Cleaning MAF Sensor

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Jonttt
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Joined: Sun 28 Dec, 2008 16:32
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  M roadster S54
Location: Liverpool

Cleaning MAF Sensor

Post by Jonttt »

EDIT: WARNING, I would advise to only try this if you are having problems with your engine (eg lumpy/rough idle etc...) and suspect it is your MAF.
My first run after cleaning as below produced a faulty MAF :head: The car had stood for a week or so since I cleaned the MAF and car started fine and ran perfectly for 70 miles. But on stopping to refuel the car would not restart :shock:
The car would actually start but not rev and idle at 500rpm for a second and die out. Turned out to be faulty MAF so I had damaged it by cleaning :roll:

It is worth noting though that the car ran fine with the MAF disconnected, just a little down on top end power but ran smooth.

So if you suspect MAF problems I would suggest just disconnecting the MAF and taking for a run (engine management light will be on but will cause no damage as car uses a "default" MAF reading). If the symptoms go then you know its your MAF and you can have a go at cleaning :wink:

On fitting a new MAF car ran "rough" for a minute hen settled down to normal. Engine Management light stayed on for another 20 miles but was off net time car was started :D

Original Post:

Although my car seems to be running fine I've read about plenty of people who have had problems that have resulted from faulty MAF sensors.

So I decided partly out of curiosity and partly for preventative maintenance, to clean the MAF sensor on my S54 engine.

Please note that the MAF sensor is c£200 to replace so care should be taken to handle it with respect :shock:

On the S54 engine the MAF sensor is connected to the rear of the airbox. On the S50 it is a slightly different design and fitting but I presume just as easy to clean.

Here is the RealOEM LINK for an S54.

The part number is 13627839014 and is common to a lot of ///M series models (ie e46 M3; M5; M6; Z4m)

Note that you will need a special "security" Torx drive to remove two securing torx screws.

Here is the MAF sensor in situ:

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Here is a security Torx Screw and driver. Note the requirement for a "hollow" in the drive meaning a normal Torx drive will not fit :wink:

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First of the two securing screws being removed:

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You then "pinch" the electrical connector block and pull it off:

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The MAF Sensor removed from the car.

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Note the sensor wire. This works by measuring the amount of current required to keep the wire at a set temperature. Air flow over this wire affects the current required. Even though this is held in the airflow after the air filter it can still get a build up of dirt deposits (or oil off an oil based filter medium) which affect the accuracy of the air flow reading and hence the fuel mixture the engine uses. This not only affects fuel consumption but can result in perceived "flat spots" in throttle response.

On close inspection this wire did not seem to exhibit any contamination but I decided to clean it anyway.

I had sourced some MAF cleaner from eBay (following recommendations on other forums)

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You simply spray this onto the MAF wires. Note do not touch the wires directly, just with the cleaning spray. You can flood the area to ensure any deposits are washed away.

The fluid evaporates very quickly. Here is a pic stright after the process following a minute of "wafting" in the air.

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It is then left for 10minutes to dry completey and fitted back to the car (do not start the car until completely dry).

Note which way the MAF is refitted:

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So its a simple 10 minute job.

Car started fine but I did not have chance to drive it :bawl: .

I don't really expect it to make much difference as the car was running fine anyway but hopefully this will help people who are experiencing some of the problems noted above to see how easy it is to try this solution yourself (ie no need to take to a garage to get your MAF cleaned). Given how simple this is there really is no reason not to add it to an inspection II type service.
Last edited by Jonttt on Tue 13 Apr, 2010 19:06, edited 3 times in total.
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Gazza
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Post by Gazza »

I've used Carb Cleaner previously, does the job :wink:
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

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aceman
Joined: Sun 01 Jun, 2008 11:16
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  M roadster S50
Location: Wakefield

Post by aceman »

Jonttt not sure from your writeup if you realise that the wire you show on the MAF is a diode or thermister probably measuring the airflow temperature. The actual maf wire (made of platinum) which is thinner than a human hair is located within the plastic housing and protected from being touched. I think to clean it effectivly you need to immerse the maf in a small pot full of IPA cleaner which will disolve any deposits on the wire.

Just thought I would mention this as it is not entirely clear from your photo's.
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aj2007
Joined: Wed 01 Aug, 2007 18:22
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  M roadster S50
Location: Newcastle-under-Lyme, Staffs

Post by aj2007 »

Jonttt

A few more in depth pictures here explaining MAF internals and cleaning, it uses an M5 MAF though

http://www.louv.tv/cars/m5/MAF/
Cheers
Ade
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Jonttt
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  M roadster S54
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Post by Jonttt »

Yep I should have taken a few more pics to make clearer.

I did not bath in a solution (not seen the article linked to above before) or physically touch the wires but followed other advice which suggested simply "flooding" with solution over a period of a few minutes (I used half of the can). This effectively aggitates the solution on the wires, first loosening and then removing contamination deposits.

I guess if you were actually having problems with the MAF you could be a little more "aggressive" in cleaning with swabs etc.. as a last resort prior to replacement. As mine is OK I did not want to risk anything that may damage it.

The pics on the link above show how it works a lot more clearly:

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As stated above I did not "swab" or physically touch the wires.
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Gazza
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Post by Gazza »

Hmmm, all I did was clean the Thermister and noticed a distinct improvement. I'll clean mine again as described to see if it can clear my flatspot :wink:
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

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S54James
Joined: Thu 08 Nov, 2007 18:53
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  Z4 sDrive35iS
Location: Essex

Post by S54James »

Hello

That picture is a in4148 diode (will double check mine) the wire is inside the module housing. you can measure the forward volt drop across a silicon diode this voltage is linear with temperature. The current is measured through the current sensing element, this can not be seen as it is in the housing.
I am a electronics engineer with over 22 years experience, so to be honest cleaning that diode will not make much difference, its the current sensing wire that needs to be cleaned. The main culprit is K&N air filters when people use the air filter oil. This oil then finds its way onto the element wire and thus the wrong reading is obtained.

best regards

Nick
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Jonttt
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Post by Jonttt »

Thanks James, I'll have another look at mine when I next get a chance.

Would be good to confirm exactly which parts are worth trying to clean (if its possible to clean them at all) :head:
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S54James
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Post by S54James »

Hello

You can check the diode with a multi meter (set it to a diode check) and it should beep in one direction only when you place the probes across the diode. The preivous comments on this thread are correct you need to gently clean the sensing wire that is in the main air flow, the more contaminated the wire the bigger the error to the main cpu. also check the sensor connector plug and socket and they are clean. On corvettes they have a burn off relay that puts a higher voltage on the element so it gets hot and burns the contamination off, bmw did not fit this on the z3m cars. If I get time I will check mine and put a step by step guide on this forum.

regards

Nick
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Jonttt
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Post by Jonttt »

Cheers Nick, I've never used a mutli meter thingy majigy :D
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markhinton
Joined: Tue 11 Jun, 2013 16:01
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  Z3 roadster 2.8

Re: Cleaning MAF Sensor

Post by markhinton »

Sorry to bring this back from the dead, but I'm going to try this on my '99 2.8 Z3 as it's making a slight ticking noise when cold, and has now developed a pretty severe flat spot. I'm dreading it's a Vanos problem, but will try this first.

What size is the security torx? And what alternative can I use to the MAF cleaner you used? Brake/carb cleaner? Or maybe this would be best suited...

http://www.halfords.com/webapp/wcs/stor ... yId_255223

Thanks!
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Del
Joined: Sat 19 Nov, 2011 18:35
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  Z3 roadster 1.9

Re: Cleaning MAF Sensor

Post by Del »

They seem keen on cleaning MAFs on a lot of the US forums - brake cleaner is considered a bit harsh - I would suggest the milder electrical contact cleaner from Halfords - used that myself.

I have experimented with cleaning MAFs and have found that once they go faulty I haven't been able to bring them back to life with cleaning - no harm in giving it a go if you want to though. From memory the BMW Z3 is a Torx ( six-point T25), I've encountered some cars that use a much rarer Torx (five-point TS25).

MAFs can have a big impact on performance and can throw vague "lean mixture" error codes etc. which can throw you off the scent. I wouldn't associate ticking on a cold engine to be a MAF problem - that sounds something like sticky hydraulic valve lifters caused by infrequent oil changes.

OE MAFs (Bosch/Siemans) are considered best but can be expensive. On one cheap little Japanese run-a-round in my extended family, I did experiment with a cheap Ebay one from the firm below and it worked brilliantly:-

http://www.ebay.co.uk/itm/BMW-5WK9605-5 ... 257c6bb573

I've also been lucky with a good OE second hand spare for my 1.9 Z3.
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Jonttt
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Re: Cleaning MAF Sensor

Post by Jonttt »

Your car will run fine without the MAF connected so just disconnect it and see if that makes a difference. If not it's not your MAF causing the problem. That way you don't risk damaging a good MAF by trying to clean it. Ps you may get an engine management light on with the MAF disconnected but it will reset itself a few miles after being reconnected :rtm:
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markhinton
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  Z3 roadster 2.8

Re: Cleaning MAF Sensor

Post by markhinton »

Thanks for both the replies - I'll order the security torx and get to work on it.

The ticking is an odd one, it's rhythmic with the amount of revs which led me to think valve lifters, possibly timing chain or vanos, but I don't know. I heard somewhere it can related to the MAF, especially since it disappears once warmed up.
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Del
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  Z3 roadster 1.9

Re: Cleaning MAF Sensor

Post by Del »

I'd try an engine oil change with Mobil 1 0W-40 - plus the filter and O-rings. Cured my quite bad sticking/ticking valve lifter problem.
markhinton
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  Z3 roadster 2.8

Re: Cleaning MAF Sensor

Post by markhinton »

It had a full service last year, but I suppose there's no harm in changing the oil. It looks dirtier than I thought it would, actually, so it is plausible that it's causing the ticking on cold starts when the oil isn't lubricating properly!
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Del
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  Z3 roadster 1.9

Re: Cleaning MAF Sensor

Post by Del »

Needs to be changed when good and hot when any "varnish" and "gummy" residues are melted and suspended in the oil. Garages often change it when cold and rarely bother to change the important O-rings on the filter "stick" which help maintain oil pressure in the upper part of the engine. The "lifters/tappets " move up and down using the engine oil as hydraulic fluid, when they stick the gap can be incorrect causing the "ticking" noise. Problem more noticeable on a cold engine when oil is thicker. Many Zs have a history of low mileage and short runs which can aggravate the problem. Despite having a garage oil change in the summer of 2011, mine got so bad in the winter of 2011/2012 that on a few occasions it would not start at all. I used Mobil 1 0W-40 which has a reputation for being "runny" and cleaning engine internals and followed with a quick succession of changes (every 6 months) and the problem disappeared. I'm back to once per year now and normal 5W-40.
swamper
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Location: Mossley

Re: Cleaning MAF Sensor

Post by swamper »

markhinton wrote:It had a full service last year, but I suppose there's no harm in changing the oil. It looks dirtier than I thought it would, actually, so it is plausible that it's causing the ticking on cold starts when the oil isn't lubricating properly!
had the same issue.....rhythmic noise ...the culprit...the valve behind the oil filter housing

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the badness makes me do it...!

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