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MAF HELL. PLEASE HELP!!

1K views 11 replies 5 participants last post by  AFaulk 
#1 ·
I have posted several threads about this car on the other forum, my last post received not a single response. I've taken it to the dealer and even they couldn't provide an actual diagnostic. They want me to bring it back and leave it for further diagnostic.

Its an 01 S55 Amg. I bought it a few months ago with a CEL light and a pretty obnoxious vibration in reverse. About a week later before I could even tackle the obvious issues due to the holiday, I had a no charge/flat battery problem. Replaced the alternator and chased down a significant battery draw from aftermarket tv/dvd installation(previois owner). That was fixed.*
CEL code indicated that the car was running too rich at idle. Cleaned maf and saw immediate improvement until the following drive cycle. CEL was back and car was running rough, idling high and vibrating in any gear besides park or neutral. Replaced maf with new bosch unit. Same situation-immediate improvement until the next time I started it up. This time however, it ran terrible for a few cycles and seemed to platue where it was no longer idling rough and the vibration was barely there/less obnoxious in reverse. Intermittently I'd feel it return, but nothing like it was before the new maf.*
Generic code scan at auto parts store- P0100 MAF Circuit A. Cleaned connection, inspected wiring at maf, cleared code. Car went through same cycle of running great-terrible-platueing. My tech read code with slightly more advanced tool- P2004 Hot Film Sensor. My tech is a family friend who runs a body shop, he does brilliant work but hasn't had alot of time to donate to troubleshooting this. Lifted carpet in passenger footwell looking for infamous k40 fuse, found additional wiring for dvd system- ac adapter, "amp" fuse and a converter box that was generating alot of heat. He removed them and capped those wires.*
Car ran the same but upon a second drive cycle (cold start) I had an rpm surge to about 1500 and stayed there then down to 1000. While waiting for him to have another opening in his schedule, It did it's same run terrible-platue cycle. This time however, I started noticing intermittent surges upon breaking. Rmps will gradually drop and once they get to about 900 they will shoot back up too 1000 before continuing to drop and you feel the jolt. At one point since this started, after placing the car in park it reved to 1500 and stayed there until I put it back into drive, then it lowered to about 700. Put it back in park and it was fine.*
Since then, cold starts seem to take more effort and upon starting it hits 1500 and then I can watch the rmp needle hunting at 900-1000. Before it comes to temp, idle feels clunky and vibration is apparent.*
Took it to Mercedes the other day out of sheer frustration and the only thing they could tell me was that I needed engine and tr anny - suspected the tranny mount due to vibration. Regarding the CEL/MAF and idle surging- all they could tell me was that the voltage to the MAF was too high even with the car off. Im a female, I dont do my own work but I do troubleshoot to help my guy along given the fact hes got a business to run too. Mercedes can't even pin this down without me leaving it for them to tinker with and Im lost in all the information I've read. My vin is as follows: WDBNG73J61A168010.
ANY HELP IS MUCH APPRECIATED.*
 
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#2 · (Edited)
This sounds like a fuelling issue and will need to be check with better equipment. Things to check are the spark plugs and wires, O2 sensors (4 in total) and the injectors. Any of these can cause the trouble you are having. If you know someone with the right equipment (i.e. SDS) they will be able to test these and more. With the test results it will be a lot easier to find and fix the trouble you have.

p.s. Could also be a vacuum leak.
 
#3 ·
This sounds like a fuelling issue and will need to be check with better equipment. Things to check are the spark plugs and wires, O2 sensors (4 in total) and the injectors. Any of these can cause the trouble you are having. If you know someone with the right equipment (i.e. SDS) they will be able to test these and more. With the test results it will be a lot easier to find and fix the trouble you have.
My tech has a snap on diag machine in which he attempted to perform tests on injectots but it wouldn't allow him to. He did test plugs and the values on 6b & 7a were in the 16-17 range compared to the other plug values of 0. Im not certain what this even meant, I imagined I would need new plugs but didn't think they held any pertinence to this issue. Why was Mercedes not able to do these tests while they had it? Would running some techron be advisable? Forgive my ignorance, but if there was an issue with fuel delivery wouldn't I still be running too rich or too lean? Id like to understand.
 
#4 ·
First up "SNAPON" is not SDS. These test take time, the dealer will want a car booked in for time charging.

The O2 sensor, knock sensor, crank ange sensor, camshaft position sensor. mass air flow sensor and the manifold absolute pressure sensor all send information to the ECU. If any of these sensors is sending the wrong information it will cause the ecu to be ajusting the mixture. A leaking/blocked injector can have a similar effect. Bad plug/leads again can cause misfire like symptoms.

So an O2 sensor that is send a lean signal will cause the ECU to hold the injectors open longer. vacuum leak can cause this as can a blocked injector, just as an example.

This is not a simple connect up and diagnose, it will take a while to test and read the codes. If you can find a good inde with an SDS and have them read the codes.

If you really want to troubleshoot this car for yourself an SDS is needed.
 
#5 ·
I'm not sure why I didnt make the connection sooner, but when you say sds, you are referring to a STAR. I got it now and yes, even snap on's greatest diagnostic machine cant do what a star can.

Duly noted, I have an appointment to bring it back and leave it Wednesday. I guess we will see what they come up with then. I appreciate you taking the time to atleast help me understand the whys and hows. I will update once I know.
 
#6 ·
You've already replaced the maf , if my workaround I suggested in the other forum doesn't work for you , I would replace all the sensors


just go ahead and change out the crank sensor , cam sensor and o2 sensors .

At this age they are all due for changing anyway
 
#8 ·
Thank you both. Tusabes, I'll look into the part numbers and prices. Salmon108, the air filters are okay based on what I was told. I'm not getting a misfire though, at least I don't believe. The car isn't reporting any misfires, if anything it is mimicking the symptoms of one while blaming the MAF.
 
#9 · (Edited)
You might want to check with Victor over at RestoreYourMercedes.com if you or your other mechanics can't sort out the issue. He's here in NYC. I've spoken to Victor over the phone several times, and while I have yet to use his services, seems to be very knowledgeable about our cars, especially electronics.
 
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