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The MAF (or Mass Air Flow meter) is an important part of a fuel injected engine, as it essentially estimates the amount of air going into the engine so the correct amount of fuel can be injected to match.  If a MAF sensor reports more air than there is, then too little fuel will be injected and power will be lost. If it reports less air than there is, more fuel will be consumed than needed, and fuel mileage decreases unnecessarily. It is also worth noting that air mass is the unit of measurement, rather than air volume, as of course the volume changes with air temperature and latitude (and especially so if a turbo is used).

IMG_3002Can it help?

I’m writing about this because I recently bought a Mercedes S500 with a misfire.  After fixing the misfire the engine is definitely within spec - masses of power, and extremely smooth all the way up the rev range. But, I realized I don’t actually know just how smooth this engine should be. Granted, it’s a V8 rather than a V12 and V8s tend to have a little more vibration at idle.  I wouldn't necessarily expect to be able to balance a coin on a V8, but could it/should it be better?

With over 100,000 miles on the engine there are loads of potential points that could introduce vibration - slightly out of spec coil packs, slightly dirty spark plugs, slightly out of spec fuel injector spray patterns, but a dirty MAF could also do this.  Some people suggest you should clean your MAF every time you change air filter. I can certainly believe that if you run an oiled air filter, but I’m more skeptical with a regular setup.  I tend to mentally file MAF sensor cleaner alongside other ‘magic’ products like gas additives and transmission stop leaks. They may work sometimes, but it’s a long shot. However, a can of MAF cleaner is usually worth the cost of admission, only a few bucks. In other words, not a huge loss if it doesn't work.

Blast it with some spray

The MAF on the Mercedes V8 is at the rear of the engine - don’t just spray the cleaner in though - in this case the important hotwire element is actually recessed - you need to remove the inner element which is held in place by 2 Torx T20 security bolts.  Then you can properly inspect the hotwire and blast it with some spray to clean it.  Mine had some some dust on it, but definitely no oil.

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Let’s compare this to the older BMW V12 design - here there are two MAFs - one for each bank of the engine. (To match the dual fuel pumps, dual throttle bodies, and dual ECUs in this car!) There’s no removable internal element here - instead just remove whole unit from car and spray the insides.  Again, both MAFs here seemed pretty clean already, some dust at best, definitely no oil.

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It's no worse!

After reassembly, what are my results? Well… I think it’s better. Maybe. Probably. It could be my imagination or it could be 5% smoother than before.  I can definitely report that it’s no worse! Sometimes preventative maintenance doesn't always produce an immediate result, but can save headaches down the road, or clear a check engine light on the cusp of rearing its ugly head.

Have you ever found MAF cleaning to be useful?

Shop CRC Industries at FCP Euro


About the Author: Bryan McPhail

IMG_2691Bryan is a longtime BMW enthusiast in Florida.

 

 

 


author image
Written by :
Bryan McPhail

Bryan is a longtime BMW enthusiast in Florida.


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