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· Registered
3,939 Posts
Discussion Starter · #1 ·
Right then...

Serviced my car today and thought I'd also clean the MAF as I was starting to get the dreaded flat spot at about 3000 rpm. I chose this cleaning option as you have nothing to loose and the cost was negligable, if it didn't work, it didn't work.

Here is the how to :-

1, Get Haynes manual and follow instructions on removal ...LOL

2, Basically disconnect the hose that runs from the MAF housing towards the engine It's one of those spring clip thingy that is a bit tricky by the way, waterpump / slip-joint pliers are good for this. Once clip is off simply wiggle the corrugated pipe off...

3, Undo the two crosshead screws that secure the MAF housing to the air box and then wiggle the MAF housing off the airbox. You have to overcome the rubber seal thats holding in it...

4, Undo the cable connector to the MAF. One of those tricky spring clip release jobbies that are impossible to explain, but careful use of a flat screwdriver + wiggling will see it come off !

5, You should now be holding the MAF housing. You now need to undo the two torx security screws that hold the MAF in place. See below for piccy. (Note:- I got that bit set from ASDA of all places for about ? 3.00 yes ? 3.00. Ironic isn't it... ASDA + Chavs + Security Bits = Crimewave ! )

Posted Image

6, Once the security screws are out, more wiggling to get the MAF out of the housing (careful not to damage the 'O' ring seal.)

7, I used some of Helfrauds (Halfords) own "Electrical Contact Spray" and simply sprayed the MAF and goodly amount of spraying I must add, just to make sure. And also sprayed the MAF housing. If you go to Helfrauds and simply ask for "Electrical Contact Spray" someone will guide you to it, much quicker that way.

8, Give things a quick shake to remove the excess spray and leave to dry..... How long ? .... You be the judge, you'll know when it's dry because it will no longer be wet !

9, Once dry, (and in true Haynes style) re-assembly is a reversal of removal, but be careful that the MAF seats into the housing and the "O" ring is ok (my O ring was blue by the way....) and be careful that the MAF housing seats back into the airbox properly and that the rubber seal is ok. Don't forget to re-connect the wiring plug to the MAF by the way.

10, Mess about for ages trying to put back the tricky spring clip thingy.......

That's it, I did take a piccy of the MAF but it turned out so blurred it was useless....

Took the car for a test run afterwards and must say the difference is astounding. Really pulls, think it's better than when I bought it. My MAF was date stamped roughly to the month when my car was built, so it's the original item.

A few thoughts and observations I've got though and perhaps you may be able to add to / answer these ?

i, Do this first before you buy a new MAF, once you've bought the cleaner (?5) it will cost nothing here in after.

ii, My own view is that a MAF is a solid state electronic item and the only thing that could effect it's operation is dirt. I do not understand how they can wear out. Maybe the resistance / resistor part of the circuit ?

iii, I noticed on the body of my MAF there was a space to put what looks like a resistor ? Could this be a potential cheap quick fix ?

If the internal resistor fails has a provision been made to fit one externally ? Does anyone know about this ? It could save lots of us ???'s if it's true.

iv, I've heard that the sensor part of the MAF has a 'special' coating on it ? By cleaning, this coating could be removed and alter the resistance of the unit ? Or... is it just something used to keep it clean(er) ? or is it a myth ?

v, I can live with cleaning the MAF every 5k when I service my car and incorporate it as another service item to do. I think now that I've done this, doing it routinely that the whole process will take less than 10 mins [not including drying timeof course]. I'm a little sceptical though as to the longlivety of it due the amount posts this item (MAF) creates. I intend to keep a close eye on things and update as and when. Has anyone else tried cleaning theirs, has it lasted, made a difference ? As I've said my car is transformed, but for how long ?

vi, My has never shown a code on the MAF and I would be interested to know what codes are given when the thing does fail ?

My guess would be it would be of the "implausable signal" type error ?

Does anyone know more about MAF fault codes ?

· Registered
3,939 Posts
Discussion Starter · #3 ·
Basicaly the MAF tells the ECU how much air is going into the engine (it's very clever, by giving the mass of air it compensates for changes in density of the air... i.e. hot day or cold day, sea level or up a mountain etc.)

So, the ECU now knowing how much air it's getting decides how much fuel would be appropriate to inject for best performance / economy. Simple as that really.

If the MAF doesn't work at all, the ECU will err on the side of caution and use a pre-programmed set of fueling values that will get you home basically. This is :- Reduced turbo boost, reduced fuelling, safe injection timing etc. = Slow car = LIMP MODE

A failing / dirty MAF (like mine was) will give an incorrect signal back to the ECU. This will usually be in the form of making the ECU think it's getting less air than it actually is and thus the ECU cutting back on fuel and boost, hence the flat spot / reduced performance. I'm convinced that this is a gradual and almost un-noticable deterioration in performance and MAF funtion. (not noticable by me until today when I found out how my car really drove)

So basically in answer to your question, a faulty MAF will effect things depending on how faulty it is, i.e stopped working altoghether or reduced operation / ability (as mine was). Both will lead to reduced performance but it is unlikely that any damage will be allowed to ocurr as the ECU is to clever for that, it'll dump you into a LIMP mode.

P.S. I'm not sure if these things pack up completely and I'm waiting to find out how from other forum members that have been through the MAF saga. My advice is start your own thread or watch the replies (if any LOL) on this one to obtain a more balanced view....

· Registered
4,149 Posts
Good guide. Although one thing I would add is some people - myself included - have got 5 point security torx screws on the maf not the 6 point like those. As yet I've not found a cheap 5 point security torx bit. I bought the Asda set a long time ago but they wont work for this [:(]

· Super Moderator
7,773 Posts
Finally got round to cleaning my maf. Can't believe how easy it is!!! Having cleaned it I'm pleased to say that it's a BIG improvement in terms of performance. It's still not perfect but it really is a lot better, just a very slight hesitation just before 3k. Would certainly recommend others to have a go if you're thinking your MAF needs replacing. Cleaner only cost 3.49!!

· Registered
2,634 Posts
At the risk of looking stupid(something I do regularly[:I]), why dis-assemble the whole thing?

What would be the reasons not to simply disconnect the MAF holder from the airbox and spray the cleaner in over the sensor, then let it dry and re-connect? It would save the need for a 6 point security torx bit....

Or would you be able to spray the MAF with the engine running (or is the cleaner very explosive stuff?) the same way you can with carb cleaner on a petrol engine?

Please be gentle if I've asked monumentally silly questions I'm new to this MAF lark....[B)]

· Registered
1 Posts
I had this problem with my TDi and did the Electrical contact cleaner trick, and it did work, but only for a short time. I ended up replacing my MAF sensor and that helped but again only for a short time. I did a bunch of research and found that minute voltage changes can affect performance drastically so I took some contact cleaner to the plug (both sides) going to the MAF and then applied dielectric grease liberally to the female plug. Then plugged and unplugged 5 or 6 times to seat it in.

The ECU has not popped any more codes and performance has returned with no hestitation at any rpms any longer.

I highly recommend this to all. Racers have been doing this for years on spark plug wires to ensure 100% of the ignition voltage is going to the spark plugs. Works for them, works for us on a slightly different application.

Side note: now I got a spare MAF when one really does go.


· Registered
874 Posts
I'm not getting any flat spots, but the fuel economy is about 10% down on normal. Haven't noticed a performance drop but maybe thats because it's been gradual.

Anyone think this could be MAF trouble?

What about Richards suggestion of spraying the MAF while still in it's housing?
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