I have done tons of searching threads for answer to this code I keep getting.I get CEL code P0171 System Too Lean,Bank 1.
I read all the threads that pertain to this and I still havent found a fix for it.Here is what I got so far and maybe somebody can chime in with some help.

I first got the code after a week of owning my 63.I opened the air boxes and cleaned all the dirt that I was amazed at finding and then removed the Charcoals and adedd K&N's.The code came back.
Now I got to the dealer and and they say replace the Intake Manifold Gasket.So I let them do that and it came back the next day.The dealer now says it must be cracked so lets replace the whole intake manifold as there must be a fracture somewhere.I say no and leave.

So now I I did a cold start up and soaked everything related to the intake with parts cleaner to see if the idle would stumble with no luck.I even did this when the car was very hot with no luck. I am smoke testing the car today stone cold and when hot to see if that will shed some light.If it doesnt what else can I look for that is making the car lean at idle?
My last impression is this : After I drive on a highway for a good while and exit the highway to my first stop light I can see the code set soon as I am idle at the light after driving.I even feel a slight rumble i nthe wheel as if onll then the vacuum leak as occurred. Please discuss and help a fellow member out.

 

Unless you're paying out of pocket and not covered by warranty, why would you not let the dealer fix the suspected cracked intake manifold? What do you have to lose trying that path?

 

I too had this code. They wound up changing the Purge Valve first, didnt help, so they changed the Intake Manifold gasket. Never got the code again.

Alot of guys get this code from the CD, and K&N's. Try putting the stock filters, and Charcoals in. See if that helps.

 

I am out of warraty.I also got this code when I first had very dirty stock filters and charcoals still in.I cant see the manifold having a crack and spraying tons of parts cleaner on it not finding it?
Also the Tech told me the manifold is a 2 piece,doesnt sound correct as the parts list just shows 1 manifold,10 bolts,1 gasket.And isnt the manifold composite and not cast?
I have digging at this forever and its driving me nuts.Is Bank1 the passenger side?

 

I just checked one of my service invoices that reflected my former faulty purge valve and the repair. The lean codes that were showing were 0745 & 2091.

I know these codes are not what the OP is seeing, I'm just providing these to show what came up for me when I had a faulty purge valve. So, my uneducated guess would be that it is not a purge valve.

 

I was told by someone who works with these cars that said the bolts may need to be replaced with ones that have some flex to them ? I'm not exactly sure but I think MB would have more information for you. Maybe ask them if there are bolts that expand more under load or with higher heat?

 

I had this code come on every ~100 miles of driving after I installed the K&N's, I have a reader, so I just reset it everytime it came on. After sending my ECU back to Eurocharged for the new v3 tune, I told them I recently put k&n's, and I guess they incorporated it in the tune, have over 600 miles since, and haven't had any CEL

 

Maybe they increase fuel supply a little in the tune to compensate for the increase in air or perhaps scale back timing ever so slightly?

 

If your not careful you can kink the filters near the back when fitting the air boxes which will cause an improper seal and a possible CEL.

 

Completely agree. I use a flash light to see if the filters sit perfectly. It's kind of a delicate little process... a PIA actually. But it doesn't take that long.

 

getting a tune might help as well

 

Well, The smoke test did not show any leaks when it was cold or hot.So I can rule out a Vacuum leak?

 

Sounds like K&Ns...i threw mine out and just use paper filters they work just as good

 

I've been using Mann paper filters. They are like 15 bucks. Not a bad deal.

 

I will put the CF ,and stock filters back in and see if the light comes back on.

 

I'm telling you man this is it. Unless you're tuned, the charcoal removal and new filters will cause the car to freak out.

 

^OK^ , I am putting it back to stock this morning.
But last question,Why is is only Bank1? Shouldn't it be both banks?

 

UPDATE: I just installed the stock carbon and air filters and removed the K&N filters.
I cleared the code and started the car and wow,no more stumble after clearing the code like before.I will kick myself in the *** if this is all it was.Now lets see if the code comes back.This is a great excuse to go drive around for awhile.

I wonder what the RWHP gains if any there was with K&N and CF removed?

 

From what I understand, not much. You're better off with a tune AND filters/deletes (because the tune will take advantage of them, not throw up) but from what I understand you're letting go of yours?

 

I always had problems on my E63 with CD and K&Ns throwing codes for lean at idle. I did eventually find out why, my oil dipstick kept being pushed up?? Bought a new one = no more codes.

Now I'am having problems with my ML63 It is throwing the same code but it is completely stock. I took it to the dealer for some transmission problems they replaced the TCU and updated the ECU, I thought it was due to that and it would eventually fix itself. Still has the lean at idle code. I am going to replace the intake manifold gasket and sparkplugs this weekend. It has just over 60,000 so it's time to replace the plugs.

 

Crap...and i just put in K and N's and CD without a tune....DAMMMIT.... so I should be expecting a code soon...?

 

Yeah buddy, too much air, and the ECU is not going to adapt to it by adding more fuel.

 

I have the EXACT same problem.

I think the problem with yours is the purge valve, they weren't made correctly to Mercedes specs so the valve can get stuck open. This valve vents gases that are captured from your fuel tank to be burned off. It can get stuck open, letting air in, hence the left bank too lean.

Get them to replace that valve and make sure its a new version of that valve.

I have replaced mine, but this code still persists, I am getting the intake manifold gasket and bolts changed next week.

This code comes on, STOCK, TUNED, K&N and Stock air filters.


BTW the above info comes from my tech friend at benz. He also said that this purge valve opens when the car sense you are doing some highway driving. I believe you said something about highway driving then the light comes on, this is why I think you have the older faulty valve.

 

Well,it has been about 100 miles now and no CEL yet.I will drive another 100 miles today and if there is no CEL then I guess I found my problem.I cant beleive it was this simple.I was thinking way to hard of more serious things it could have been.Even the dealer and other wrencjers alike wanted to dig deeper and start replacing big money items.I should have came to the C63 section a long time ago as I knew there were many modders here rather than the E63 guys.Lesson Leraned,"so far".

 

Problem solved. It has been 300+ miles and no CEL. I do believe the issue is that with K&N alone there is no way for them to SEAT properly as the CF would help them make a better seal.
I find it strange as this only affected Bank 1 alone though.That's why I was thinking to hard on what the problem was.If I got both banks I would have determined the filters quickly to be the problem.None the less all is well and she purrrrsss well. Thanks guys for the insight on this issue.I also hope this helps others when they use the search button.