What do it do? - PeachParts Mercedes-Benz Forum

chomamma · #1 09-05-2007, 09:41 PM

There is some type of air control on top of my filter housing. Looks like it has gotten hot shown on the upper side of the pic. Maybe something electrical burned out. Sorry It's a bad pic , but the best I could do at night? What does this component do? It has electrical connectors going to it and I suspect may be some of volume control for the intake?

I have finished rerbuilding the turbo and have not been impressed with the performance. Seem doggy. Does this component restrict airflow? Thank.s

Jeremy5848 · #2 09-05-2007, 09:46 PM

Quote:

Originally Posted by chomamma

... What does this component do? It has electrical connectors going to it and I suspect may be some of volume control for the intake?

I suspect that you are correct. It has a flap connected to a potentiometer, which feeds a signal to the engine control brain, tells it how much air the engine is ingesting. If it gets jammed, it will restrict air intake and more importantly, limit the amount of fuel the brain allows the FI to pump. That could cause your symptoms.

Knightrider966 · #3 09-05-2007, 09:47 PM

I don't believe this is designed to restrict airflow, but works as a temperature sensor. How many wires does it have going to it?

#4 09-05-2007, 09:49 PM

That is the airflow meter. The father of the MAF sensor on modern engines, it is for calculating the amount of EGR gasses to flow into the intake.

Take the airbox cover off and make sure it moves freely. It should spring back but it should not be hard to move.

chomamma · #5 09-07-2007, 08:58 AM

Well, I am trying to improve my performance on my 2.5. When I bought it, the turbo was frozen so I rebuilt it. Turns freely with goo vacuum to wastegate. EGR is temp disabled along with some air control valve on the intake tube. I just tied it up so the butterfly is always opened. Now perhaps I am expecting more from a turbo diesel, but it still seems to really poor in performance. I'll do a 1/4 mile and check the times. Also I thougt about checking PSI in manifold during 3000 rpms.

But does this air box sensor imput signal to increase fuel in anyway? Could it be bad and not tell IP to send more fuel? What determines more fuel, just a mechanical linkage? ALDA still attached.

#6 09-07-2007, 08:34 PM

Disabling the EGR on that model will cause the computer to kill boost and engine power.

2.5Turbo · #7 09-07-2007, 09:03 PM

The airflow meter has nothing to do with the fuel quantity. The only connection between the computer and the IP is the rack position sensor and idle speed actuator. Your right foot and the ALDA are the only two things regulating the fuel. This part is only for the emissions control devices. It feeds airflow data to the EDS computer which then decides how much to open the EGR and flapper valve between the turbo and EGR. As was stated before, if the EDS computer finds anything wrong with any of the sensors, it will cut boost and store codes. Even if you put the EGR back and untied the flap on the airflow sensor, it would still be slow because the codes would still be set and no boost would build. Do a search on here for the schematic for a code reader that costs about $20 in parts from Radioshack. With this homebrew device, you can read the fault codes and easily clear them as well. It's an indispensable troubleshooting tool for a 124.128 owner; somewhat equivalent to the mityvac for the 123/126 and older crowd

Just hope that melted plastic was caused by an external thing and not the sensor frying...they cost more than you'd think.

chomamma · #8 09-07-2007, 10:03 PM

Ok I have hooked it all back up. I never tied the flapper on the airflow only the butterfly on the intake tube accross from the egr. What does this valve do? disconnecting egr keep turbo from boosting. Does it open wastegate? I put boost gage on intake and although it is a 100 max scale, It didnt' budge.

So I'll be going back to two things. When I rebuilt the turbo, It scraped on the compressor side and the only fix I could come up with was shiming the housing. Must have shimmed too much or maybe a intake manifold leak. But I doubt I am leaking that much if any. Maybe a shot of ether around it can determine it. I also may have swithed the vaccume lines going to the egr and the buterfly thingamabob valve. Do you guys know which valve above the airbox controls either of the egr or thingamabob butterfly dohicky whatchmacallit?

lietuviai · #9 09-07-2007, 10:16 PM

The melted spot looks like someone left a hot drop light on it. Ask me how I know.

chomamma · #10 09-07-2007, 11:34 PM

Can believe there is anything in it that would get hot....