This response makes be think that the answer to the single most important question I have right now may be no?
Will driving the car with the exhaust issue cause further damage?
Assuming that there is simply a hole in the exhaust headers or cats, the sound I'm hearing is more annoying than an indicator of engine damage?
I imagine the chances that the puffing sound is coming from the main engine block is low?

 

The good news is your fuel pressure is perfect
now the bad news is:
here is one of your problem ....

12.2V while driving...


marginal voltage

Fixing this is going to help your chassis stabilize performance. Don't rush at changing perfectly good ALT... the culprit is with ECU painted GND.

Can you learn to display Battery voltage on your instrument cluster... we want to see what the AMPERAGE shows when voltage does it's yoyo.

Use similar engine warm conditions around the neighborhood.

At the end of the day the workaround temp fix is to disconnect the ALT Control connector and check you get near 14v.

Currently voltage goes up and diwn with engine deceleration, this is normal.

What's not normal is deeping below 12.55V... we see 12.2V: THAT IS LOW VOLTAGE draining batteries including AUX if present.

This may very well be your RPM surge or the fault on ESP module can cause that as well.

 

Overall it's a fairly clean report. The only concern I have is with ESP due to AIRMATIC issue. This can impact ECU ability to use CAN-C .
The radio and TPMS are in CAN-B... mostly unrelated to ECU besides SAM for Batt sensor.

 

You never did a test drive when buying this used car ?

 

I did. The broken cv axle and broken coilover were so bad (NOT safe to drive) that I was distracted from everything else.

The main thing is the older mechanic in the shop that did a pre-purchase inspection gave the engine a listen (AT IDLE ALBEIT) and said "that's a healthy engine"

I told the shop that did the pre-purchase that as long as the engine and trans are healthy, I'm entirely okay with fixing everything else myself. I'd just rather not do engine or trans work.

My research on the M273 and 722 AT gave me the mindset that I'd have a decent chance at a rebuild project considering I bought it at ~90,000mi

 

I'm glad you said that because I would have instantly replaced the alt without thinking twice.
I'm not sure how to do that (voltage on instrument cluster), but I'm familiar with people who "code". I have an openport that I can spend the day getting setup?
Is amperage from alt a metric that the ECU measures? I could put an ammeter between the alt + and the cable that leaves it?
Ok, I can disconnect the alt control connector and measure, no problem.

Thank you for all of these insights Cali! I will continue to chip away at this day by day.

If there was a way to buy you and Juan a case of beer or coffee or a meal it would make me very happy to do so.
I deeply appreciate the time and effort you both have given my posts. Thank you.

 

hey guys, maybe post a pic for the ECu gnd that needs cleaning to get good contact? that will help him locate and get to it.. Also the ALt control connector-- a pic will help.the OP.

 

I have a can of automotive electrical contact cleaner. I can go and do it tomorrow.
I'm still concerned about not driving the car because I don't want to cause additional damage.
Curious how I can get a definitive answer on that question.

 

By the way, I have this OpenPort OBD dongle https://mbworld.org/forums/e-class-w...u-version.html
Would getting Xentry PassThrough setup help with diagnostics for my situation?

 

Poor ECU control of LIN Alternator leads to low voltage.
The shortcut is to unplug the ALT connector to get 14V internally regulated by ALT itself.

control connector slot

> ALT uses 2 cables:
-- 1 large cable bolted on: don't touch big red!
-- 1 small connector: unplug that one!

Measure voltage with engine runing : 13 to 14V.
Confirm poor voltage problem solved?

Fixing that involves a time consuming GND cleaning campaign. First i suggest to learn to display battery vitals on dashboard using steering wheel keys.

Having a good power supply will let your chassis operate under normal conditions.

 

I used the Foxwell scanner (dramatically higher quality) and it had a menu to read "Drive system Live Data" of which "Alternator" was an option
There was a bunch of information on the alternator like its load and other metrics. Voltage read 13.9-14.2 roughly while idling.
I'm happy to take photos of the scanner if you like. I feel alternator voltage is likely GOOD/HEALTHY based on what I saw.

 

LARGE current spike after initial startup. Is this typical behavior????

After a quick short run to the grocery:
Voltage stabilizes to 12.6V
Is this normal?

 

Yes, that is the STUPID NORMAL how MB programs the alternator charging intervention. In the name of "green" eco bull-shiet.
That is why I disconnected the LIN cable to alternator to prevent ECM from doing that intervention, and let the alternator own built-in charge regulator does its
normal charging method..... which is so much more civilized and will never allow under 13.8V.
The charge regulator manages the current throttling so very nicely, not the voltage.

 

low voltage but charging!


High 75AMP CHARGE ABUSE


scary HIGH batt charge amp

Overall I did not witness active drainage ie. negative current.

Battery was obviously discharged but nothing prive ALT caused that.

Your voltage from 12.6 to 14.9v is well controlled during video capture.
So long it never gets negative the alternator is always supplying your car as it should.
We did not see active drain...


> OVERALL:
Keep an eye on display while car is in 12.6V float mode after driving 40mn, engine warm:
1- voltage should not drop to 12.3V !!!
2- Amp should stay positive and small.
3- 75Amp means batt is deeply discharged

 

I don't mind implementing this change on my car if the community here generally agrees that the pro's outweigh the cons.

That control signal plug does look like it might be challenging to get to so thank goodness it only needs to be done once.

 

Thank you Cali!
I will.
If I see this 75A draw after I start driving it daily, I assume that's an indicator of an issue?
I currently don't drive it besides to make posts here (scared of causing damage until problems resolved)

I assume that if I learn how to code the car's computers with my OpenPort and Xentry via passthrough I can make that voltage and current display appear normally without having to put the dash into service mode?

If I get ALL of the gremlins evicted from this vehicle I will put a high current draw sound system in it. Alternator production and voltage information are critical with this kind of system. I will obviously upgrade the car's electrical (AGM and possibly H/O alt and big 3 if possible) if I get this far. All of this is fantasy talk until the drivetrain is in a healthy and reliable state.

 

The stock Bosch voltage control is smart but as implemented by MB it can lead to odd chaos. These is what causes weird Gremlins non-sense.

Don't rush to temper squarely with the charging system. It is perfectly good design at 12.6V float.

Unplugging ALT LIN is a quick-shortcut when you need to drive but not a fix.

The car does not need 14.4V.
It only needs the ALT to supply 100% all current with low impedance.
12.6V float renders the battery nicely "transparent" once it is fully charged. It works perfect when no significant current (-5Amps) flow out while driving.

Keep your eye on both Voltage and Current wth the dash. Painted GND posts can cause the ECU reference to royally drain any battery to 11.xV. followed by 90Amp yoyo.
These bugs are carefully manufactured in every W212 - No parts necessary ✌️

​​​​​​
The one thing you can rush at fixing is your main GND STRAP at the carriage bottom near muffler.
Simply double it up... done with that game!

 

The single one thing that tells me charge system is okay is I did not witness any negative BATT. current.
We do see nasty 75Amp from Batt being drained prior to starting: user caused.

That means ALT was always supplying positive charge current into battery, never negative current.

That's all we want.

 

Further confirmation.

How difficult is this job? The videos I see of exhaust header / manifold work always seems horribly difficult due to access to the bolts/studs and the tremendous heat seizing them.

My gut is telling me to have a really good shop do it and tell them take their time doing a good job, some extra billed labor is fine for quality work?

 

@mgiara I'm curious if you were able to resolve the issue and how?