Hey Gilly..MAF Sensor... - PeachParts Mercedes-Benz Forum

99ML430 · #1 06-07-2004, 11:59 PM

Hey Gilly......l apoligize if this is a repeat question....but no one seems to able to answer the question as to why a Cold Air Intake causes the Check Engine Light to come on...is it really just the oils from the filter or the extra air that causes the light to come on.....l tried a CAI , and my MAF sensor had just been replaced the month prior.....it was fine for a day, then the CEL came on..ls there really any possible way of re-setting the MAF to except more air.....l've had CAI's, on all my prior vehicles with no problems, is this just a situation of the MAF being too sensitive to change....Any idea's Gilly...l would love to make this CAI work.....

Gilly · #2 06-08-2004, 08:50 AM

Hi
I'm not all that familiar with CAI on an ML, love to see a picture, maybe you can link me to a seller.
If it involves a washable media filter, that is what I believe the real problem is, it's contaminating the MAS. I don't think the MIL is being CAUSED be the intake charge being colder at all. Can you try doing this with a dry media filter somehow? Are you in the position now where you need to replace the MAS? If you can't try a dry media filter, you can try just really lightly oiling the filter.
The MAS is really a rather "dumb" device and cold/warmer/wetter/drier won't really affect things. Eventually it gets worn out or contaminated, then the readings are screwy and the mixture ends up being wrong. Well, eventually the mixture ends up being off anyways. The engine operates the mixture cycle to get correct readings at the O2 sensors, but it uses the MAS to "predict" what the mixture should be, and normally it's all very efficient. If the little film matrix in the MAS gets either worn, ie "pitted" by dirt (caused by a bad filter or air intake leaks), or a load of this filter oil gets on it, you get bad readings and eventually a check engine light (MIL or CEL). This all courtesy of the Federl Gummint, o'course (OBDII).
Hope this helps a little, let me know if I can try some other questions. You may be able to clean up the matrix and reuse the MAS, not really anything I've ever gotten in to, but if you're the one buying the new MAS, it may be worth a try.
There is a thread I think in this forum about doing just that (cleaning MAS).

Gilly

Gilly · #3 06-08-2004, 08:59 AM

Just as an aside, remember the actual "CFM" of air isn't what you are changing with a CAI. The CFM is pretty limited by the displacement of the engine and engine RPM, it can only suck just so many cubes. What you are changing is the MASS, assuming you truly are getting colder air. But I maintain you are too limited by ambient temps (temperature the air happens to be that day) for a CAI to do much good, unless the manufacturer really bumbled and the intake charge is really heating up alot before getting into the engine. And besides that, how much is the air gonna get heated up before hitting the innards of the engine? ALOT, that engine is HOT baby! Maybe I'm wrong, maybe the air is running through there so fast that it doesn't heat up that much.
But as far as the MAS not being able to "handle" the CAI, just remember about the temperature of the air if you were to drive your truck say an a -10F day up here in Wisconsin. You wouldn't expect a check engine light if you did that, would you? And here you are affecting the temperature very very slightly if at all. It can handle CAI, I'm from Wisconsin, you can believe the ML can handle sucking in cold air!

Gilly

99ML430 · #4 06-08-2004, 11:18 AM

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&rd=1&item=2481225667&category=38634

Hey Gilly..here is the link..What do you think......

Gilly · #5 06-08-2004, 12:44 PM

I think it's all BS.

mparker · #6 06-09-2004, 06:45 PM

Gilly

Right to the point! And, no sugar coating!

2000 E320
Brilliant Silver
Ash

Gilly · #7 06-09-2004, 09:27 PM

Damn skippy on that!

Gilly

99ML430 · #8 06-09-2004, 10:53 PM

Hey Gilly...Just a follow-up..l put the original air box back on, and "Poof" the Check Engine Light has disappeared....So that tells me , the MAF sensor wasn't dirty..........and there must be a controlled limit of air the MAF will accept....

Gilly · #9 06-10-2004, 04:48 AM

Nope, something else is going on. The CFM's are controlled by physics: engine displacement X RPM. Mass is controlled by nature: ambient temp and humidity. You can run it without a filter or airbox at all and it won't be affected, assuming the air can move freely through the filter. ANYTHING you do to filter the air is going to RESTRICT airflow, not improve it. Some may be less restrictive than others, but things have got to get pretty bad before you'll notice any change in performance (clogged filter for example) There's no way you can "improve" the airflow, short of maybe some weird sort of supercharger, that is going to affect the fuel injection system.
Did you ever find out what the DTC was for with the check engine light?

Gilly

99ML430 · #10 06-10-2004, 11:39 AM

Gilly....l will find out what the error code is..and l will let you know...Thanks so much for trying to figure this out for me....

Gilly · #11 06-10-2004, 06:23 PM

I also just want to say that it is pretty weird that you'd have this "ppof" event when reinstalling the original airbox, so I will freely admit that no one "knows it all" so maybe there is something strange going on that I've never come across in regards to the mixture control in general or the MAS in particular which may be setting the light. TYPICALLY if it is a mixture problem, being caused by a "bad" MAS, or lets "think outside the box" and say it is a filter issue, the check engine light wouldn't just clear out immediately. So I'm thinking it may be a coincidence that the check engine light is now gone. It can eventually, after a few days time, clear the check engine light, but not immediately like that. So anyways, it would be best to have the codes in the engine control unit read sometime soon, there should still be a stored code for whatever the reason was for the light to come on.

Humbly yours
Gilly

99ML430 · #12 06-14-2004, 09:30 PM

Gilly..one more question......l e-mailed the supplier, and he told me that when l unplug the negative battery for 30 minutes, that l'm also suppose to unplug the MAF sensor, the question l have "is from where ?"....is it connected to something else....l saw that it was attached by these funny looking screw heads, but l thought that it what held them on....any thoughts...

Gilly · #13 06-14-2004, 09:53 PM

I think he means to disconnect the electrical connector from the sensor.
But this won't matter, neither will disconnecting the battery, this is all false. Even if disconnecting the battery did turn off the light, what would it prove to discoonnect the sensor?
Is he trying to tell you to do this so he doesn't have to provide warranty on the part or what?

Gilly

tabo · #14 06-17-2004, 02:18 AM

Gilly, those washable knn air filters require spray of oil around it after you wash it.. I think that oil is causing the MAF's sensitive wire to be dirty and covered, also I believe the knn air filters don't do a good job in filtering the dirty air.. so more dirt and pollution goes through the air mass sensor compared to the oem paper filter.. Never use knn air filters or cold intake on a ML, cuz it'll cost you $500 to replace the air mass for something that doesn't really speed up your car..

Gilly · #15 06-17-2004, 10:52 AM

The ME control system does not use a wire in the sensor, that type of sensor is called "hot wire" and was used in the old LH system (LH standing for Luft Hotwire). The sensor used in the ME system is Hot Film, it is the same as used in the HFM (Hot Film Management) system. The ME system is essentially the same as HFM except the ignition system is built into the conrol module, integrated fuel and spark systems.
At any rate if you read the posts you will see that I already pointed out (in my first post) that yes the problem with K&N or other washable/reuseable media filters is that the oil can contaminate the MAS. I believe they are efficiant in reducing airflow and good at filtering, but not to any great benefit. The main advantage, and the reason they are really around is that they are washable/reuseable.

Gilly