Air Mass Meter / Sensor for 1999 CLK 320

Are you sure you need to replace it? My 1998 was throwing code P0170 which, among other things, could be a bad air mass meter. Over six months I replaced a number of less costly possible causes, but it looked like the air mass meter needed to be replaced. A few weeks ago I took the air mass meter apart and gave it a thorough cleaning with carb & choke cleaner. I figured that since I was going to replace it anyway, I had little to risk by attempting to clean it. Within a few hundred miles, the CEL was off and the car runs great.

Ditto.

I had the same experience with the AMS on my '97 E320 straight six.

A very very careful cleaning eliminated the codes etc. with no return of the problem.

Did you guys reset the computer to clear the light?

My car has almost 55000 miles on it, and I have read that this is about the time that the air mass meter goes bad. But I will try the cleaning first.

What carb and choke cleaner did you use?

Any advice on how to take it apart and put it back together? Special precautions / tools needed?

Many thanks.

Steve, how did you take it apart? I am told it needs special tools to open the tamper-proof torx screws?

My car had done only about 37K when the check engine light came on so a failed sensor was unlikely. Code PO170 didn't describe the exact problem so I paid the dealer to diagnose and estimate the repair and its cost - MAS about $550 - $600. (On line part price $260.) Then I thought about the project and decided to first try cleaning the MAS and replace it DIY if cleaning failed.

My E320's MAS has two pieces: the larger 3" x 4" "stovepipe" housing and the sensor itself which screws into the side of the "stovepipe".

Removing the "stovepipe" is easy. Then one removes the sensor from the "stovepipe".

I used an old fashioned (smoker's) pipe cleaner to simply clean the sensor's wires - very, very carefully, in daylight.

I didn't use any solvents for there are no petroleum deposits on the sensor.

Cleaning worked, there's been no further messages.

I cleared the codes with my code reader.

Do you need special TORX bits to remove the screws? Where do you get those?

Thanks.

A while back I had bought a set of security bits. They've come in handy for everything from the car to McDonalds happy meal toys (don't ask.)

This is the set I got. I don't remember where I bought it.

I did nothing to clear the light. Just drove it and it cleared itself in a few days (I drive > 120 mi/day.) You can reset the computer by disconnecting the battery, just make sure you have your radio code handy.

I used carb&choke cleaner to clean it, and the whole job took about 20 minutes. Just be sure not to touch any of the sensor components.