BenzWorld Junior Member
Date registered: Nov 2002
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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 â€śmisfiresâ€ť. My SA estimated a minimum of $500, but I asked him bluntly, what part needs to be replaced? He responds, â€śprobably the spark plug wires.â€ť 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 â€śstalling,â€ť â€śidle problems,â€ť 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 SAâ€™s suggestions of replacing the spark plug wires. Again, based on the information on this site, I picked up the Karlynâ€™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 SAâ€™s scanner now reads P0171 and P0174. â€śLike I saidâ€ť he blurted out, now itâ€™s the MAF. At the same time I said, â€śThatâ€™s another item I can replace myself.â€ť 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 Iâ€™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.