MAS Sensor location - PeachParts Mercedes-Benz Forum

Tom Q · #1 10-14-2003, 01:49 PM

Where is the MAS sensor in a 95 C220? My idle is going up and down and I want to clean the contact first as a temporary remedy.
Help.

#2 10-14-2003, 06:09 PM

Irratic idle may be due to a vacuum leak, check as many vac lines as possible and around the air intake tube joints, if possible get a can of propane and spray where you think it may be leakiing and the idle will increase if a leak exist.

Gilly · #3 10-14-2003, 09:57 PM

It's right by the aircleaner, plugs inline between the air cleaner and the duct tube.
It's not a MAS sensor though, it's a MAF sensor.
MAF= Mass Air Flow sensor.
People always call it a MAS sensor, I guess that's calling it a Mass Airflow Sensor sensor. If you have to call it a MAS, then drop the second "sensor".

Gilly

Tom Q · #4 10-15-2003, 12:37 AM

thanks for the info guys. I'll go ahead and check the MAF sensor. Also, about the can of propane spray, where can I buy this? Do I spray it while the engine is at idle

I have 125K miles on the car and I doubt if the 02 sensor has been changed. Would a bad 02 sensor cause idle problems?

blackmercedes · #5 10-15-2003, 12:49 AM

Do you have a check engine light on?

Tom Q · #6 10-15-2003, 12:52 AM

check engine light was reset because I disconnected my battery when I changed the plugs. It hasn't lit yet.

blackmercedes · #7 10-15-2003, 12:57 AM

Quote:

Originally posted by Tom Q
check engine light was reset because I disconnected my battery when I changed the plugs. It hasn't lit yet.

Bummer. I think on OBD-I systems you erased the stored codes as well. They would be very useful in diagnosis. You need to figure out the problem before spending a whack of cash on parts.

Tom Q · #8 10-15-2003, 01:40 AM

my car is OBD-II certified but I don't have a diagnostic tool. Dealers are asking for $ 85 just to read the codes. Does anybody live in the modesto area who can help me?

blackmercedes · #9 10-15-2003, 03:30 AM

A place like Auto Zone can read rudimentary codes for you, but won't provide any diagnosis. It's a free service. You might start there and see if we can help solve the problem if it's an obvious code. You may end up at the dealer or specialist indie in order to get a truly accurate diagnosis. However, in the long run, that will probably save you money.

Gilly · #10 10-15-2003, 06:31 AM

The codes usually won't erase that easily on an OBD2 car, I'd still get the codes checked just in case, as previously mentioned at AZ or something. The MAFS or O2 sensor don't really make sense for this problem, sounds more like something with the throttle motor. If it happened right after the plug change, I'd concentrate more on the air intake leak problem. I'd look at that duct tube (cross-over tube that runs over the valve cover)over on the drivers side of the engine where it goes into the throttle motor, see if the tube dropped into that rubber ring properly, not pinched or part of the rubber folded in.
You only notice the problem at idle?
Can you describe the problem a little more clearly? How much does the idle fluctuate, and is it doing it very frequently, or like every 5-10 seconds or what?

Gilly

Tom Q · #11 10-15-2003, 02:18 PM

Gilly, sometimes it would change the idle and sometimes it just stays at 6-700. I also feel like something is pulling me back while I'm driving (rpm between 2500 - 3000). Also, the car sometimes shuts down as I approach a stop.

I changed the plugs because of this symtom hoping to solve the problem. Today, I opened the door locks and opened the right rear passenger door. I heard a hissing sound coming from the door mechanism and I heard the vacuum pumping longer than usual. Could this be one of the causes of my problem?

Tom Q · #12 10-16-2003, 07:18 PM

I repaired the leaking door lock pump and cleaned the MAF. So far so good. I'll observe the car for a week. Thanks guys