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Replace MAF (HFM5)...NOT! Save money and clean it...

Discussion in 'E39 (1997-2003)' started by ViolinARC, Feb 5, 2009.


Is MAF/HFM5 cleaning a decent DIY?

Great info...I found the procedure very helpful and saved money. 1 vote(s) 100.0%
Stop wasting my time, just spend the bucks to replace it. 0 vote(s) 0.0%

    ViolinARC guest

    Post Count: 178
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    Replace MAF (HFM5)? Save money and clean it...

    This is part of the thread that I started on BF.c a while ago to clean the HFM5 sensor on my 2000 540iA M62TU. I hope you all find it as helpful as the thousands of others who read it there...;)

    (1) Simplified instructions...you need a Torx T-20 Security bit, a can of CRX MAF Cleaner and your brain. Look at your air intake tube (post air filter) and you will see a unit with electrical harness attached. It should have two Torx T-20 security screws holding it to your intake tube. With all electrical off (I didn't disconnect my battery and all was fine), disconnect the electrical harness from the unit, then use the Torx T-20 Security bit to remove the screws, gently remove the MAF (noting the direction of the sensor wire and plate), take a can of CRX MAF Cleaner (ONLY use this cleaner), place it on a clean cloth and spray the unit throughly (until the cleaning fluid looks clear). Once it's clean, allow it to dry COMPLETELY before reinstalling the unit and energizing it (starting your engine). CONGRATULATIONS, you have just completed your task and saved about $300+. It won't perform like a 'new' unit (as pointed out by someone earlier in this thread) but will be FAR better than the function of a dirty unit. It will even stop the CEL from appearing on your OBC.

    (2) Quick update on the procedure. The first time I cleaned the MAF, I ONLY sprayed it down throughly. This time I went one extra step and actually wiped down the sensor wires (VERY gently) and also used the end of a toothpick (slightly "shredded" to act like a brush) to wipe down the sensor plate as well. What a difference it made! I could see the dark oily stuff (not a lot but it only takes a little to offset such a sensitive device) coming off the sensor plate on the light colored wood of the toothpick. Actually, I would recommend you use a q-tip soaked in cleaner to do the sensor wire and plate. IMO and from my experience, just spraying the unit will be a minimal cleaning with limited results. GL...

    Please feel free to post any and all results from trying this procedure...

    (1) Another update...pre-MAF cleaning average mileage was 19.7MPG with an average speed of 37.9MPH and after cleaning my MAF for the second time (more throughly this time) my mileage is reflecting the change. I am now averaging 19.9MPG with an average speed of 37MPH so as you can see my MPG is going up as my MPH is going down. It should be just the opposite...clean your MAF FTW!!

    (2) EDIT: Another update on fuel consumption...after today (same route, cheaper gas and more traffic as usual) the average has jumped to 20.6 MPG with an average speed of 36.6 MPH so you do the math! HAPPY HOLIDAYS!

    (3) A reset when cruising at 80+ MPH reveals that I'm getting 26.7 MPG on a straight, flat run. 24.6 MPG at 90+ MPH (keeping up with moving traffic BTW) and my average after today's 125 mile round trip down to San Jose is, 21.1 MPG with an average speed of 38.5 MPH (MPG's were higher but traffic came to a dead stop a few times on the way home, which lowered my average). Not bad for 15 minutes of my time...

    ***Go here if you want to read about all the others who found this a useful and positive DIY.

    DISCLAIMER: I, the OP, can not and will not be held liable for any possible damage incurred from the improper execution of the above suggested procedures. Thank you...

    GregS_WI guest

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    Good info

    Good info. Did the same last summer when I did the plugs. The car ran much smoother, but couldn't say which of my two maintenance items did the trick.

    ViolinARC guest

    Post Count: 178
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    Thanks...thought I'd share the info cause it's such a quick and easy fix with incredible results. If anyone else experiences success with this procedure, please let everyone know what an amazing money saver this is. The hesitation is gone and she still lights up the tires after this cleaning...

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