So, as the title says, I have the 2 codes, P0170 & P0173, that are almost always a bad or dirty MAF. At the same time I changed out the number 5 coil pack I replaced it with a new Bosch MAF sensor in the old housing and it was great for a few days, then a shudder on start-up and the codes have returned. I'm thinking it's a vacuum leak somewhere in front of the throttle body, but I haven't been able to find anything. Any ideas?

 

I'd say almost all of the MAF inserts sold are fake. The best source to get a new MAF is from Autohausaz or A Mercedes dealer (Much $$$).
From these two sources you get the complete unit (sensor + housing ).
Did you try cleaning the old sensor?

 

I haven't yet. I'll try that tomorrow. It worked fine at first, and now it seems only to cause problems at startup. I thought perhaps that was related to the secondary air injection pump but I'm not getting a code to indicate that the SAI is bad.

 

I actually got the full housing and it has all of the correct Bosch numbers on it, but I didn't realize that counterfeits were that prevalent. Any good way to tell the fakes apart from the real thing?

 

This might help:
https://mbworld.org/forums/e-class-w...f-sensors.html
And:
http://www.benzworld.org/forums/w210...o-sticker.html

Good luck

 

Swapped in a clean, original Mercedes maf. Still same problem. Seems to be at its worst when it is at idle just after startup. Still can't find any vacuum leaks. May try a ecu reset and see if it comes back right away.

 

Did you clear the codes?
Try driving around, sometimes the codes will disappear and the systems will adapt to the new change.
To completely reset the ECU, TCU, fuel trim adaptations I'd unplug the battery overnight and see.

 

Unplugged the battery and reset the computer; the used MAF works fine, though there is a bit of lumpiness to the idle. Drove about 50 miles- no codes yet.

 

Glad everything is fine.
After reset/battery disconnect the ECU needs to re-calibrate it self. That's why the car may run slightly poor the first few miles.
Yesterday I got the codes P0100 & P0110, maf sensor has less than a year on it from a reputable source.
I'm waiting for a sensor from AutohausAZ this time.

 

Sorry to resurrect this thread but P0170 and P0173 seem to be
infamous codes for most models.

Question is Does changing a New Maf sensor require
the battery to be Unplugged to completely satisfy the
fuel adaptation and rid of the CEL???

 

No. Over time the ecu will adapt but a battery pull reset seems to help speed this process along quicker. If the MAF is not your problem then you will see new codes after reset and MAF, helping with troubleshooting.

 

Thank you for the info. Codes have been reset few times
but same Codes have returned but haven't tried the battery solution as yet.

Local dealer wanted $200 for diagnostic test, indy goes for $106.
been told could be 1. fuel filter, 2. 02 sensor, 3. vacuum leak
At this point I have no other codes. This car is very sensitive
when not fully functioning!?!?!?!?

 

I chased down a P0170 code for a long time. Mine ended up being a vacuum leak and CEL came on when the engine was warm/hot. I had 2 leak spots both coming from the air intake manifold in which I had to uninstall and reseal the entire intake and perform another hose repair that came out of the intake manifold . I went through the same process of MAF, filter and I even thought of the 02 as well.

Check all air and vacuum hoses for rips tears or brittle connections. If all else fails, you may have to suck it up and pay for diagnosis.

 

I came to believe that P0170 is one of the tough ones.
Anyways, this past Sunday I risked taking off the elbow duct hose which connects between TB and Maf sensor
pretty tight space where the elbow attaches to TB, I cleaned around using CRC Maf cleaner and also cleaned the elbow.
Long story short the new air filter housing was Never installed or seated correctly when shop worked on it, reason being is
the air box was Not seated all the way down where it meets the circular seal on the Maf sensor I discovered it when taking
things apart no wonder CEL has been on last month. The air filter housing is Not so easy to properly install without some force.

Once I satisfied everything is properly put back I then erased stored codes and re-read it the P0173 was gone....at least for now
but the dreadful P0170 is still there so reset the code once again and took it for short spin we'll have to see what will happen next couple of days
knock on wood that it will not return. Acceleration from stop light seems somewhat noticeable much much better I even got to 80mph.
Here's a brief of what has started on my car.
1. Initial codes P2006 and P0218 early this Feb.
Parts replaced, a new IM, a Thermostat and a Map (later code)
2. P0170 and P0173 followed. At this point, the car has gone back to indy shop at least 5 more times for more troubleshooting.
one occasion, car made audible high pitch sound upon normal acceleration due to small air leak. Shop claimed air filter housing
leaked air around seams so a new one put in and seemed to cure the high pitch sound but the 2 codes are still.
Car has been used daily despite CEL on for the entire episode.
3. A brand new Bosh Maf sensor was installed by me after watching some Diy videos.
This is Where it got even twisted, ...I stress, whenever you need to remove the air filter housing, you Must Ensure that it sits flushed
all the way down when you put it back, feel around the circular seal and there should be NO gap anywhere even check the elbow air inlet duct.
I went further by replacing the 2 air inlet hoses, well, one of them was in a bad shape from Ebay but Mercedes's.
oh, I finally was able to clip that clamping piece wire over the air filter housing ....that's when you know your air box is correctly in place with your Maf sensor.
ok, this's getting too lengthy....will report upon progress, thank you all for reading, enjoy driving your cars.