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Discussion Starter #1
Have a problem & worse I'm away from home & on the road stuck, so I really need to solve this !

Car has been driving perfectly, went 40 miles up interstate just fine and after exiting at a stop light
flashing check engine light, terrible idle, won't accelerate, exhaust smells of incomplete combustion..

MY 1ST ACTION INSTALLED NEW BOSCH CRANKSHAFT POSITION SENSOR it was 5 years old and
a cheap easy part to replace

It made ZERO difference so please don't suggest this CPS part ty

Whatever failed had a pretty immediate effect and I had to tow it to a parking lot.

I made a YouTube video of the idle hoping someone has had this same failure & KNOWS the fix
https://youtu.be/ui1AOcWGmuM

Thanks
 

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If you don't mind sharing your current location, someone may be nearby with a Star setup. Otherwise, you'll be getting a lot of guessing. So sorry you're away from home with this problem!

Sent from my SM-N960U using Tapatalk
 

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Discussion Starter #5
location

If you don't mind sharing your current location, someone may be nearby with a Star setup. Otherwise, you'll be getting a lot of guessing. So sorry you're away from home with this problem!

Sent from my SM-N960U using Tapatalk
West Palm Beach, FL
 

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OBDII scan shows Code P0300 random misfire
Hi,

Not much help from me I'm sorry to say ......................

Sadly this is the trouble with simple OBD Readers, yeah, ok, we can all here it is misfiring, hence the P0300 code, but I'll be willing to bet there is other Codes in there that only SDS or a really good $1500 upwards Generic will see :(

It is these Codes, and or some live Data that we need to see to give an accurate diagnosis ;)

I can tell you what isn't wrong with it ....................

Crank Sensor :devil

If I was in the area you are I would happily come out and plug it into SDS for you ;)

I hope someone will be able to help you soon :wink
 

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Did you try turning the engine off and back on? Normally the random misfire is also followed by the codes of the individual cylinders that misfired as well (if I recall correctly). Is it possible there are other codes that haven't been read?

I've learned on my W211 that a flashing check engine light means misfire detected. Once the misfire is detected, the car will shut that cylinder down.

Random story:
This may sound odd, but my W211 would misfire pretty much on queue when I drove it East Bound on Goerge Bush Turnpike - about a mile before my I-75 south exit. I would never misfire anywhere else, nor when traveling West bound. I kid you not - the strangest thing. Engine would be half power, shaking the car like crazy and all. I would normally take the first exit off the highway and find a safe spot to shut down the engine and restart. That normally would get all cylinders firing again and everything was back to normal for the rest of the drive.
 

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If you don't have a code scanner readily available and want to try it just fire it up unplug the mass airflow sensor see if it makes any difference try unplugging coil packs to see if they make any difference and if you unplug something like that and it doesn't make a difference that's what's wrong with it so if you unplug the mass airflow sensor and it runs just the same if better than it's the mass airflow that's bad mine Ran terrible with it plugged I and I d unpluged it and it would actually run way better
you will need a better code scanner so you can better address which cylinder is misfiring and why..
I use a bluetooth code scanner with the torque app and it has been very useful for me identifying any issues I get. Even tells me which cyl is misfiring so I knew exactly which plug wires popped off. Also let me know when my mafs values weren't accurate even though it didn't have any mafs error codes present . The real time data readings are a big help. It will tell you if 02s are working and heating properly and all. I use an elm327 or something cheapy like that and the paid fir torque app to read and erase the codes. The app can be used from your phone but i run mine off my pioneer head unit because i like to see the metering effects
 

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Mass air flow or bad coil pack would be my guesses but it could really be anything like a shorted wire

You will probably need to take it to a mechanic there’s lots of Mercedes mechanics in the West Palm beach area
 

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Discussion Starter #10
NO JOY

Okay still not drivable.

UPDATE got better scanner and the misfire in cyl 5,6,7,8
half the engine is not running properly.

Have tried disconnecting MAF and it makes little to no difference

I replaced 8 spark plugs on the drivers side bank NO DIFFERENCE

What ever malfunctioned has interfered with 1 side of the engine and I wonder
where the electrical harness that goes to coil packs for the cyl 5-8 connects to.

The Benz shop did replace the motor & trans mounts a few months ago is it possible
that jacking up the engine or areas that they were working has any connectors tubes or sensors that can make the car run so terribly that it can not be driven?

WHAT EVER HAPPENED WAS SUDDEN with check engine light and immediate loss of power and stalling with accelerator doing very little to keep engine running.

My car is still stuck 60 miles from home and I'm out of ideas !!
 

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Discussion Starter #12
I felt the exhaust output from both pipes and they feel the same also if I run the rpm's up to 3000 it seems to smooth out a bit, does this seem like it could still be a clogged cat?
 

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Have you looked at fuel trim values? Only way to evaluate exhaust back pressure is to remove front O2 sensors and install pressure gauge.
 

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1) I felt the exhaust output from both pipes and they feel the same also if I run the rpm's up to 3000 it seems to smooth out a bit, does this seem like it could still be a clogged cat?

2) UPDATE got better scanner and the misfire in cyl 5,6,7,8
half the engine is not running properly.
Hi,

1) That tells you nothing, they are both connected via an X piece at the rear end of Transmission Tunnel :wink

2) IIRC, the Coils LT side are individually Earth Triggered by ME but there is a common positive supple to 4 coils on each bank, (if I don't recall correctly then it will be the other way around, +ve triggered with common Earth), my guess is that this "Common" has failed, on some cars I've seen a coil fail and blow a fuse ............ Not sure if the MB has fuse for this, first, pull a plug lead, stick a spark plug up it, earth to head etc and see if you have spark, or check with small 5w test bulb for a good solid LT + /- ve to that bank of coils :wink

If you do have a good common + / - ve and a spark, then the Injectors on each bank work similarly, so check the feed / earth to them ;)

HTH,
 

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Discussion Starter #15
Hi,

1) That tells you nothing, they are both connected via an X piece at the rear end of Transmission Tunnel :wink

2) IIRC, the Coils LT side are individually Earth Triggered by ME but there is a common positive supple to 4 coils on each bank, (if I don't recall correctly then it will be the other way around, +ve triggered with common Earth), my guess is that this "Common" has failed, on some cars I've seen a coil fail and blow a fuse ............ Not sure if the MB has fuse for this, first, pull a plug lead, stick a spark plug up it, earth to head etc and see if you have spark, or check with small 5w test bulb for a good solid LT + /- ve to that bank of coils :wink

If you do have a good common + / - ve and a spark, then the Injectors on each bank work similarly, so check the feed / earth to them ;)

HTH,
I did take a new sparkplug and put it on the A lead from a coil pack and it was generating a spark. No guarantee if it was proper.

Wonder if a stuck open fuel injector can cause this. Did u see & listen to video ?
 

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Discussion Starter #16
interesting

Hi,

1) That tells you nothing, they are both connected via an X piece at the rear end of Transmission Tunnel :wink

2) IIRC, the Coils LT side are individually Earth Triggered by ME but there is a common positive supple to 4 coils on each bank, (if I don't recall correctly then it will be the other way around, +ve triggered with common Earth), my guess is that this "Common" has failed, on some cars I've seen a coil fail and blow a fuse ............ Not sure if the MB has fuse for this, first, pull a plug lead, stick a spark plug up it, earth to head etc and see if you have spark, or check with small 5w test bulb for a good solid LT + /- ve to that bank of coils :wink

If you do have a good common + / - ve and a spark, then the Injectors on each bank work similarly, so check the feed / earth to them ;)


HTH,

I have WIS, how can I find about the fuses that handle the power to the right & left banks of injectors & coil packs You say the 3 conductor clips that go to the individual coil packs are +5v +5v & ground since each coil has A & B spark plugs.

This is helpful info
TY
 

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Hi,

Yes I watched your video.

No, above I did not specify Voltages at the Coils, they are actually fed from a single Fused 12V, but jointed for each Bank of Cylinders ........... see below ............

If you have a good Spark then you have likely lost a bank of Injectors, to be safe buy a set of "Injector Testing Noids" to plug in and get someone to Crank the Engine over while you see if they flash as Engine turns ;)

Injectors are 2 wires and each Bank appears to have Injector pin 1 going to a common connection sleeve Z7/35 for ckt 87, broken wire at connector sleeves can happen !!
I cannot see any Fuses involved in Injectors, the trigger wires (pin 2) go back to ME ECU :wink

Coils are 3 wires, and Fused in the Right Front (F1) Fusebox they share the same Fuse for all coils which is a 15A f49 this then feeds to where 4 coils join together at connector Z3/29, (there looks like 2 of them just to confuse things), Z3/29 (1) and Z3/29 (2) for left and right banks.

The L & R Coils 12V+ are jointed (terminal pin 2) at Coil #4 for 12V+ supply to the opposite bank.
Again these joint are worth a look to see if one wire is broken off if you suspect that the Spark is not good.

Coil Terminals 1 & 3 pins go back to ME ECU, is this possibly PWM control for spark intensity based upon torque load but I :dunno: for sure !!

You need to look up the Engine Wiring Diagram in WIS, (like I just did), and the exact location for the Z7/35 and Z3/29 connections in Star Finder .............

This isn't an exhaustive diagnosis, my whole point is that it just seems far too much of a coincidence that you have lost all 4 Cylinders on one bank so look at what is common to all of those Coils and Injectors ............

HTH,
 

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Discussion Starter #18
This is the WIS ignition system diagram.

I know there is a solution but I've never have had one be so elusive and not obvious !
 

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Discussion Starter #19 (Edited)

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