SeaCoupe

When it rains it pours. I just did the tranny flush, and tranny cooler line replacement, and now this:

I was noticing hesitation under light load. Say 2,500 rpm. It felt ever so mildly like hitting the rev limiter, but VERY mild. So, I went to Autozone and rented an OBD-II reader. (cost $189.00 - I get the money back when I return it.)

I couldn't get the code to come up for a bit, when finally I got:

P0171 System too lean Bank one.

Having gone to Buellwinkle's website: http://www.buellwinkle.com/MBOBD2.html

I was able to see that this indicates a faulty mass airflow sensor. So, the plan is to uninstall it, and try cleaning it with say CRC Airflow sensor cleaner. Maybe I'll get lucky that way. If that doesn't work I'll be buying a new one.

I gotta say, I'm having a bit of tough luck with this car right now. I'm about to hit 120,000 miles, and I can't beleive the silly things I'm encountering.

E

CarLAB

E,

hopefully its just a dirty sensors..good luck.

Regards

Darwin W

516mbtek

airmass sensor

516mbtek

ohh never mind u have a 230k...um there is a hose from under the intake manifold that connects to the throttle valve area...its hard to get to but it often leaks then eventually will break and the car will not run. It is likley just starting to leak vacuum causing your lean condition (adaptation)

SeaCoupe

Thanks, I'll check that out. I did just have a pressure transmission line get hacked up. So, I thought by chance the tranny fluid could have worked its way into electronic connections.

Trouble with all this, is not working on the car. I actually enjoy that. It is finding the time to R&R the piece.

E

SeaCoupe

Well, while driving into work this a.m., I did get the Check Engine Light (CEL).

Damn, at least I know my engine and can feel things before the system wants to tell me.

E

mig888

Hope the sensor cleaner works for you, but I do agree with the above, most likely a leak - you're in socal, do you know any connections with the dealers to get a % off parts? Lemme know if you don't.

SeaCoupe

Well, here is the outcome. First off, BIG thanks to Buellwinkle the King of the W203 forum! He helped me with some email exchanges to dial me in.

The test drive shows a good improvement in throttle response. My little tick of hesitation at load didn't reappear. This little fix didn't take a whole lotta time. Took more time to go to Kragen to get the CRC MAF cleaner ($5.99).

I think I do have a problem though. There is a lot of oil that you will see in the pics of the air piping. That MAF was filthy! So, now I need to figure out why I'm getting oil in the intake. Something tells me S/C. This happened at 94k miles. But I had the S/C replaced. If the S/C seals need rebuilding I'm going to have the unit ported. Anybody have a recommendation on who to have the porting done by?

So, here is the Picture testimonial.

The MAF is on the drivers side of the engine on top. It connects to the line with two Torx screws (15 or 20 size), and the other side has two hose clamps.

It was a little tough to get to the bottom Torx screw on the underside, but when you take off the hose, you can swing the piece a bit over towards the fender. So that will give you access.

Unplug the MAF from the harness by squeezing on the clip's side holders. This wil come sliding right down.

When you have the MAF out, don't touch any of the inside surfaces. I used the CRC spray liberally attacking the outside flanges, then moving to the inside of the flanges, and finally making sure that the two element looking bits were shiny again.

Let it dry. During the drying process I was busy using a clean rag to clean the inside of the air piping. Again, I don't know why I have so much oil in there, but I'm going to find out soon. When the MAF dried I reinstalled the piece, and put the electrical connector back on.

Finally, I hooked up the OBD scanner to the port under the steering wheel. Using the scanner I erased the code, and went for a test drive. At the end of the test drive I checked for the Error code, but I got a PASS from the reader.

So, that is it. Hope this helps someone in the future. Again, I want to thank Buellwinkle for walking me through this. I really appreciate his help. If I can be of assistance to anybody, don't hesitate to ask.

I'm going to get on a small soap box here. I notice that threads with,

What 20" wheels should I get?"

receive FAR more attention than the tech ones. This is really too bad. You guys could save a bit of money by taking the DIY route.

E

drexappeal

E,

So sorry to hear you're having issues with the m111. Your car is still fast as hell. Anyway, seems really odd to have oil leaking into the air hose. I'd say, now that you took care of the error code by cleaning the MAF, your number 1 priority should be finding that leak. Seems kinda strange to me that the oil would be gathered where it is (by the pics that you have). My first thought is if there was over flow and a slight crack in the hosing that allowed the oil to get in, but there also would've been oil all over the air box and engine covers. If I think of any other possibilities, I'll let you know.

BTW, you're right about the responses to "non-technical" threads. I think the main reason is due to there being so many different types of w203's coupled with a lot of the members not having much knowledge that could contribute to helping you.

Either way, there are the few knowledgable ones that do have extra knowledge, so hopefully those people can help you come to a resolution with the issues.

Buellwinkle

Doesn't seem odd at all, there's a check valve that goes to the intake and is used to recirculate crankcase vapors back into the intake. But as it gets old it rots inside and stops working and oil can get sucked into the intake. I know what it is on my 1998 SLK230 but the 2002 has a slightly different motor. I'll see if I can find out what it is.

This is where it is on my SLK230 with a similar motor -

516mbtek

sry drex i wa refering to the 271? motor duh.. dont forget to clean out the intercooler if it has not been said or oil on maf issue will reoccur

pwimezza

Here is code that came up PO171 System too lean Bank1.
Now I hear under the foot of my car in that area like a hissing sound.

chuang

I have a 2004 C230 (sedan), what's the part number of that hose, and how do I verify whether it's that hose that is causing the problem? I did a "visual" inspection and didn't find any visible "leaking" of air around those hose or rubber areas...Now after I reset the CEL light, it will come back on with P0171 code couple of hours later... thanks!