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Marty
Marty, Mercedes Technician
Category: Mercedes
Satisfied Customers: 53780
Experience:  Bosch Certified Master Tech. Over 35 years experience.
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Recently had replacement of evap canister valve with

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recently had replacement of evap canister valve with connector wires, purge valve and couple of hoses at the evap canister performed by MB dealer. Then I had 2 other codes popped I think they were P0171 and P0175. The dealer indicated that there could be some issues with fuel pump and air intake. After research I had replaced MAF sensor with aftermarket unit. The car indeed start running much smoother, but i still get MIL come on.
I recently acquired AUTEL Maxidas DS708 and performed some tests. I can attach printout results if needed. What I get is (576 selfadaptaition in idle speed range, right bank of cylinders 1.126) and (596..... left bank...1.126). I read somewhere that selfadaptation reset may need to be performed after MAF sensor replacement , but don't know how to do it and will this aleviate the problem. As I mentioned before, the car runs really well, nice and quiet, except when cold,engaged in drive but standing on traffic light. I feel very light that goes away after a little drive. Then even at the stop, the car is extremely quiet.
Customer: replied 4 months ago.
I may be mistaken on P0171 and P0175 as I am trying to remember and not 100% sure.
Customer: replied 4 months ago.
i am attaching correct error codes scanned from the obdii
Customer: replied 4 months ago.
ops wrong file, here is the correct one

Hi, sorry for the long wait on this question. I have been away a lot over the holidays. You should be able to reset the self adaptions on the Autel. Even if you don't reset them they should eventually come down to normal range after driving the car about 20 miles or so. Your fault codes and adaptions indicate a fault with the fuel mixture on both sides of the engine (too lean) at idle. If the MAF sensor was the problem your adaptions should have come down to around 0. It looks to me like you still have a vacuum leak. Since both banks are affected I would look for a leak at the MAF connection to the intake. Ideally you should smoke test the intake system to locate the leak. If the car runs well I don't think you have a fuel pump problem but a fuel pressure test should be performed if you find no vacuum leaks. The aftermarket MAF sensors can also be problematic. If there are no intake leaks and the fuel pressure is good I would try an OEM MAF sensor. Also, if the pump were the problem your adaptions at partial load would also be high. Your part load looks good.

Let me know if you have any questions.

Marty

Customer: replied 4 months ago.
Thank you.
I just ordered genuine BOSCH MAF sensor. Will wait to take additional steps until after it's installed.
Then we may have a clearer picture or, at least, will be able to eliminate some of the probable causes.
Regards,
Alex.

You're welcome, Alex. I'm leaning more towards an intake leak based on the adaptions.

Customer: replied 4 months ago.
Hello again
Yesterday replaced MAF sensor for original BOSCH. Today received the same codes, but the readings were much more closer to required. Still need to find the source of the issue. I am attaching 2 pictures for your info.
Customer: replied 4 months ago.
Also, sometimes in the morning I hear hissing sound when releasing brake pedal. I have read somewhere that this could be due to the leaky brake booster vacuum hose and it could also be the reason for my issue. Is this true?

It certainly appears that there is a vacuum leak. The brake booster could definitely cause this problem. If you suspect the booster you should disconnect and plug the booster vacuum line then see if your adaptions start to drop. Ideally you should smoke test the intake system and check the fuel pressure.

Customer: replied 4 months ago.
I think i found the problem. I traced vacuum line from break booster to the manifold(i think that is what it called) and the place where it enters the engine cracked. I am attaching 2 pictures. What are your touts on this?

The picture is too close up. If that's a vacuum or breather hose it will definitely cause the problem.

Customer: replied 4 months ago.
It's the plastic (not rubber) hose that comes from the upper front part of break booster and goes to the engine. Here is a better picture.

I can't see the broken part in that picture. Take a picture with your finger pointing at the bad area.

Customer: replied 4 months ago.
It's very hard to get there, tight space all the way on the back of the engine. I put yellow arrow.

Ok, take one more from pretty far away and place an arrow so I can get an idea of what I am looking at.

Customer: replied 4 months ago.
This is the best I could do. The hood is too close to the body. It's right by the windshield.

In your second picture, if the hose you are pointing at is the one that is split then that is your problem.

Customer: replied 4 months ago.
Here is the drawing for better understanding.
Customer: replied 4 months ago.
It is not the hose itself, it's the aluminum entrance of the manifold (that is part of the manifold itself) it's cracked.

If it goes to that booster hose then it is your problem.

Just checking in. Did you ever get this problem resolved? Did you replace the booster hose?

Customer: replied 4 months ago.
Hi there,
The hose looked ok, but there was a crack in the hose entrance into intake manifold. Rather than replace manifold, I wanted to see if it can be fixed. So I ordered Devcon Plastic Steel Epoxy. Just got it last night. Will try to take care over the weekend. Hopefully this will take care of the issue. Otherwise a new manifold is my future.
Thank you,
Alex.

Sounds like it's worth a try. Let me know how you make out. Please don't forget to rate my service in order for the website to credit me for helping you.

Customer: replied 4 months ago.
Will definitely do.
Thanks.

You're quite welcome.

Customer: replied 4 months ago.
Still the same codes pop up. Next step to disconnect brake booster to eliminate internal problem. Then I am not sure yet.
I will keep you posted and will definitely rate your answer at the end.
Thanks.

If you can smoke test the intake system that would be best. You could also spray all around the intake with carb spray with the car idling and see if it picks up any vacuum leaks. It's not as good as a smoke test but you might find something.

Customer: replied 4 months ago.
Don't have the smoke machine, but did the carburetor cleaner spray and found absolutely nothing. I do hear some hiss when releasing break pedal after hard press. Otherwise the breaks work just fine. Could it possibly be EGR valve? When car is cold it feels and sounds fine on idle, but i get hesitation and occasional jerkings when transmission is engaged but car stopped at the traffic signal. Also I feel somewhat hard acceleration. All symptoms go away after about 15-20 minutes of drive when the the car heats up.

Your problem is that the car is too lean at idle. If the EGR was open it would misfire and you would get EGR fault codes. You are just getting mixture codes at idle speed. A vacuum leak is the most likely cause.

Marty and 3 other Mercedes Specialists are ready to help you
Customer: replied 4 months ago.
My suspicion is that something expands when the car heats up and stops the leak, but I can't figure it out.
Also, after I come home in the evening and the car is still worm, all the numbers are pretty good (including self adaptations on idle speed, around 0.890) except for Lambda control upstream TWC [600 G3/4 right o2 sensor before TWC KAT signal] and [602 same for the left sensor] the numbers should be between -0 and 1, but fluctuating between 90 and 600 very rapidly. Will do some research on that.
Customer: replied 4 months ago.
I think I just found the culprit of all of the issues. Break booster has constant hissing sound when the engine is running. I bent down under the dash and pulled back the rubber boot that covers the break pedal push rod connecting to the booster. There was a constant stream of air and a lot of oil or something of that nature. I have also done some reading on this matter and tink that this is the cause of the problem. Will order a new one today. Hopefully will not be that complicated to replace it.
Customer: replied 4 months ago.
Hi Marty,
I have replaced the power booster and also replaced brake fluid over this weekend. The codes are gone now and everything seem to work fine. I really appreciate your help. Although I still have some humming sound when accelerating on the road, it's absent when accelerating on idle. Don't know what could it be. Also the error 114 The sensor rotor adaptation in the load range 2 and engine speed range 1 is learned. Basic adaptation must be performed. is still there. MIL light is off. I am going to rate your answer right now. If you have a chance, let me know what the rotor adaptation means and how to perform it.
Best regards,
Alex.

Hi Alex, sorry for not replying sooner I did not see that you replied to me. The rotor adaption calibrates the crank sensor to the ring gear. You should be able to go into adaptions in the Autel and find the option to perform the adaption.

Customer: replied 3 months ago.
Hi Marty,
After replacing power booster the engine works fine it is very quiet. The only issue I have is early in the morning when it's cold it feels like too much torque at the traffic light, the Car is shaking a little, but very quiet in neutral. I think there could be transmission issues. I have never changed transmission fluid and the car has 155000 miles. This coming Sunday I will try to replace transmission fluid, rear and front differentials and converter box. Hopefully the problem will go away.
Thank you for your help.
Alex.

I agree with changing the fluids but I don't think it will help for this problem. I would suggest checking the transmission mount and motor mounts for this problem.

Customer: replied 3 months ago.
But the car runs normally after about 15 minutes of driving. If the mounts were lose I would be experiencing shaking all the time, wouldn't I?

I thought you said it was rough at idle. Another possibility would be the ignition wires, coils and spark plugs. Bad wires or a bad coil or spark plugs can give you an uneven feel at idle.

Customer: replied 3 months ago.
I will change all of the fluids and see if it helps. Hopefully it does, but if not, I will have to continue my quest.
By the way, there is no option for performing adaptations for my particular car w163 on Autel MS708.
Do i really need to perform the adaptation or this doesn't affect performance?

The adaption is not mandatory. It just fine tunes the misfire detection capability of the ECU.

Customer: replied 3 months ago.
Thanks.

You're quite welcome.