Mass Air Flow (MAF) Sensor Replacement - Mercedes-Benz Forum

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post #1 of 61 (permalink) Old 08-07-2006, 11:10 PM Thread Starter
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Mass Air Flow (MAF) Sensor Replacement

Hello all--this site and its members have been so helpful to me that I thought I'd share my experience with a recent idle/stalling issues on my '02 ML320.

My experience started with a rough idle at stops or in park. It felt like it was stalling and/or wanted to die during idle. Since there was no Check Engine Light (CEL) on, I brought the car to the dealership. Since I have a good rapport with my Service Advisor (SA) he plugged in a scanner and it indicated “misfires”. My SA estimated a minimum of $500, but I asked him bluntly, what part needs to be replaced? He responds, “probably the spark plug wires.” After he cleared the CEL light, I politely said thanks, but not thanks for now. I then performed a search on this site on topics of “stalling,” “idle problems,” etc. and it returned all sorts information and at the same time, confusion on my part as it suggested all sorts of things to replace. Others have experienced replacing the spark plugs and wires, MAF, fuel filters, and even engine mounts.

I decided to take my SA’s suggestions of replacing the spark plug wires. Again, based on the information on this site, I picked up the Karlyn’s and I installed it myself. The replacement process took about an hour and I consider myself lucky because the wires pulled out relatively easy. After the plug wire install, the idle was a bit better, but not as smooth as it should be. I brought it back to the dealership and with the SA again using his scanner, it produced no error codes. My SA then said that with past experiences with these types of symptoms, the MAF may be the next to go. Well, two weeks go by and my CEL finally comes on. The sad thing is that I was actually looking forward for that darn CEL light to come on.

I brought the ML back to the dealership and the SA’s scanner now reads P0171 and P0174. “Like I said” he blurted out, now it’s the MAF. At the same time I said, “That’s another item I can replace myself.” No problem, he said and I can probably get a non-OEM on the Internet for less. I asked my SA how much it would cost for the part, he said around $385 for consumers, and a bit less for mechanics, or wholesale purchases. I then asked him how I can get my hands on one of his scanner and he responded that unless I’m doing this (fixing cars) for a living, the one they use is an overkill for me, and expensive. He recommended that I pick up a simple OBD II scanner. As usual, I searched this forum and one member recommended the Equus 3100 series.

I know that there are others who have posted on how to replace the MAF, helpful, but no pictorials. Attached is a PDF document with pictorials--a bit of an overkill, but I hope that it is of use to some.
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File Type: pdf Mass Air Flow Sensor Replacement.pdf (684.3 KB, 7980 views)
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post #2 of 61 (permalink) Old 08-07-2006, 11:32 PM
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I bough original Bosh MAF on ebay for $150. That was with no pipe, what cost me additional 2 minutes to cut slots on tamper-proof screws.
Nice pictorial, but I have mixed feelings.
Is somebody needs pictorial to release 2 spring-clamps and one screw, maybe he should take it to a mechanic?
BTW the CEL clears itself after few restarts.
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post #3 of 61 (permalink) Old 08-08-2006, 02:12 AM
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Thumbs up

There are always someone who needs a bit of help with the first attempt even at the simplest jobs.
Nice guide for those in doubt by RestyB.
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post #4 of 61 (permalink) Old 08-08-2006, 02:27 AM
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Add MB & Bosch partno's in your pictorial to round it off! ...

PS: The pics are not sharp enough to recognize the numbers.
Attached Files
File Type: pdf MAF - M112 - remove&install.pdf (65.9 KB, 3222 views)
File Type: pdf MAF - Service Info - Diag.pdf (3.3 KB, 2478 views)
File Type: pdf Air Temp Sensor - Diesel - Engine 613 (ML270CDI).pdf (190.3 KB, 1264 views)

Last edited by pleubner; 08-08-2006 at 02:47 AM.
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post #5 of 61 (permalink) Old 08-08-2006, 06:28 AM
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Howdy RestyB,
Long time no post huh! and now suddenly you've share your experienced how to replace MAF sensor. Good job Home boy and Thanks;-)

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post #6 of 61 (permalink) Old 08-13-2006, 12:23 PM
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What did you pay for and where did you get your Equus 3100 series scanner? I'm in the market for one too, but there are a lot of options out there. Did you review other scanners as well? I've been doing research on and and would appreciate any comments.

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post #7 of 61 (permalink) Old 08-30-2006, 11:11 AM
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Thank you for a very informative pictorial guide!

BTW, did anyone find the need to diconnnect the battery for 30 minutes to reset the Adaptive Driving Parameters after MAF replacement?

"The true delight is in the finding out, rather than in the knowing." - Isaac Asimov

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post #8 of 61 (permalink) Old 08-30-2006, 04:53 PM
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You can get the MAF inserts from german star dot come for 150.
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post #9 of 61 (permalink) Old 08-30-2006, 05:00 PM
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I just installed one on my E last week or two weeks ago. I purchased a used one from Potomac Auto ($135, I believe) just to make sure I knew what to do. I pulled the old one out and plan to clean it. The I found out later (like onesixthree pointed out), that one can get just the insert. My advice is to get the insert from Bosch, put it in and you'll be good to go.

The CEL didn't just disappear - it's a sampling sensor. Just give it time - mine selfadjusted after three/four days of driving.

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post #10 of 61 (permalink) Old 08-30-2006, 07:04 PM
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Anyone tried cleaning the maf? I'm still on the original maf with 97k miles and have yet to trigger a cel light. I cleaned the maf with rubbing alcohol last summer and again this year with a 'crc maf cleaner'. I just bought it to see if it works, but at least I don't have a cel light AFTER using this thing..
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