I have extensively troubleshot this and I'm stumped. I replaced my intake manifold. That part appears to be fine. It never misfired before my manifold replacement.

The connectors to cylinders 1 and 4 were so stubborn that they took the connector part of the coil pack with them. I super-glued them back into place and cylinder 1 was misfiring when I got it back together. I scraped out the connectors in case some glue got onto them. It ran fine so I parked it.

I ordered two new coil packs because I didn't want to rely on super glue.

It drove fine for a few miles into my short commute until a cylinder started misfiring. In the parking lot at work I pulled off the cyl1/cyl4 coil pack connectors and put them back on again. It ran fine to get me home.

The replacement coil packs arrived and I swapped out the two glued ones, reconnected them, and cylinder 1 was misfiring. I cleaned up the connector again and it ran fine so I parked it.

A couple of days later I went to drive it and is was missing a cylinder again at startup. I disconnected/reconnected again and it got me to work today.

Most of the drive home was fine. I gave it full throttle and cylinders 1 and 4 are started misfiring again. I limped it home.

I can't get either cylinder to fire again.

• I have not touched the spark plugs in a year.
• I swapped the adjacent coil packs 1(new)-with-2 and 4(new)-with 5. ECU codes always say cylinders 1 and 3.
• I disconnected the battery for a reset. ECU codes didn't clear. Cylinders won't fire.
• I disconnect and reconnected the ECU
• I scraped out each of the four wires in each connector
• Wiggling/disconnecting/reconnecting while running doesn't produce any change.

My best guess now is that the connectors on the harness are faulty.

Replacing the harness is possible. Does anybody have any ideas before I go that far?

If this was an injector issues would I be seeing other codes? I doubt it is the injectors because my coil pack wiggling revived it a couple of times.

 

This has turned into painful experience. You can tell the coils have outlived your engine, all of them should be renewed at once. Now is a real good time to deal with spark plugs.
I don't know If I would trust hand crimped only ignition wires, solder is better.

 

I replaced the spark plugs a year ago without incident.
I'm talking about buying a complete harness and replacing it. Most of it was disconnected for the intake manifold replacement.

 

Harness replacement is a rather expensive option.

 

Found a few on ebay for $150-200

 

Yours is M272 engine, correct ? Attached ECM wiring diagrams.

At the least......
Check the ECM side , the wired connector which has the female terminals. Test it for good fit. This is low power signal for COP trigger.
From cylinder 1 to 6, ECM connector M, pin 6, 8, 7, 30, 32 and 31.
That one at ECM is a mini female terminal, only usually 1.2 millimeter wide....while the COP side gets 2.8mm wide terminal





Power wise, those COP does not get any power from ECM, its all from wire harness which is from N10/1 Front SAM.

Fuse 23 if for cylinder 1 to 3




Fuse 22, if for cylinder 4 to 6





I am not familiar with M272 ground system for engine electronics,. but when you open up intake manifold, it may be that the ground connection was not tightened properly, the Z6/z6 & Z6/z5 (splice ) from W16/5 ( ground stud ).
The W11w2 and W11w1 is a feed back ground to ECM via capacitors for noise control, that is also important, I can create mild misfire when I disconnected this equivalent wire on M276.8 from one of my COP., but mine does
not have those capacitors ( one per bank ).



Splice connection has a DOT in a square, they do not show the actual interconnection but that dot means it is connected to a few other wires, you must observe it well.






Clean well the X26 connector which also handle the W16/5 ground wire interconnect and the interconnect for positive power for COPs which are the splices called Z7/35z2 and Z7/38z2.



Good luck.................

 

ADDING W11w1 and W11w2 ground points, in PDF, attached.

Your M272 X26 interconnect connector no 1 and no 2 is below :




I think these 2. Sorry me not familiar with m272

 

Can I ask why you replaced intake manifold?

Are you sure no air leaks?
When you take coil connector off does the wire move enough that it upsets a connector to something else?

 

Because it is a rapid solution to the flap issue that happens with ALL of the higher milage cars. I am nearing doing the same thing on my E350.

 

Agree it is a common issue with these engines, M272/M273; however, replacing the intake manifold has been the source of misfires or rough idle (worst than before) in the past because :
1 - the seal between the manifold is not perfect
2 - broken brittle vacuum lines during the process
3 - Pending vacuum lines to be connected
4 - else for any lengthy process: a lot parts in/out during that replacement.

 

@S-Prihadi Thank you so much for the detail. I'm consuming it to the best of my ability.

The first thing I understood was the ground. There is a ground lug on each side and both were in place. I removed and cleaned them. That didn't make a difference.

I get the feeling that it is something mechanical. Something is moving it in and out of operation. I was mostly losing cylinder 1 before and 4 sometimes. The first time I floored it both cylinders 1 and 4 stopped firing and haven't fired since.

As far as physical movement the ECU, harness, and coil pack all move together. I don't see anything flexing or moving.

I'm off to look at the pins on the ECU connector and check continuity to the coil pack plugs. Carefully removing and reinstalling the harness may expose a damaged wire.

 

Question: Does the ECU stop trying to fire the missing cylinder, requiring a restart?

 

@S-Prihadi Again, thank you so much for your help! I checked all that you described.

• The ground connections were clean and tight. I cleaned them and made them tight to no avail.
• Coil pack wiring
  • Signal pin #4
    • Cylinder 1 pin #4 has continuity with ECU pin 6
    • Cylinder 4 pin #4 has continuity with ECU pin 30
  • Pins 1-3 - each bank is connected together and cylinders 2,3,5,6 are working, so I checked continuity with other coil pack connectors. Continuity is all there.
• I previously swapped coil packs with the adjacent cylinder and the problem stayed with the cylinder. This proves the coil packs themselves are working.
• ECU pins are clean and straight
• ECU connector looks fine.

I started removing the harness like I did when replacing the intake manifold.

• don't see any physical damage
• no bare wires shorting together.
• I popped open the plastic casing - the capacitor is intact (and it serves all three cylinders, the other two are working)

I tried to disassemble the coil pack connector but I don't know how to get it apart without destroying it. I have a set of those pin removal tools. I got the wire boot off but I can't get the plastic insert out. It looks like there are four tabs that keep it snapped into place.

Could it be the connectors themselves? I could try to find a couple at a junk yard and splice them in.

 

Question: Would the injectors not firing cause the same code? When it is running with the missing cylinders I can smell gasoline from the exhaust. It is rather strong.

ECM codes
0629 Combustion misfiring has been detected.
0633 Combustion misfiring of cylinder 1 has been detected.
0637 Combustion misfiring of cylinder 4 has been detected.

OBD2 codes
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0304 Cylinder 4 Misfire Detected

 

Usually yes. At times DTC must be deleted, before it can resume normal operation.
DTC may come late.

 

The ECM definition of misfire is this simple fact :



.




If injector or COP is disconnected, say from a damaged wire , there will be DTC stating short circuit or open circuit.
If intermittent bad contact at say injector or COP, the misfire counter can be used, but the DTC may come later, after some cyles.

How are the 6 spark plugs condition at the moment ?

 

Did you replace the fuel injector seals when you transferred the injector rail to the new intake? You stated you noticed a strong odor of fuel coming from the exhaust...pointing to a problem with the injectors imo.

 

Did you do this kit or did you do stand alone parts?


https://www.fcpeuro.com/products/mer...ierburg-516475

 

Yes I replaced the six lower seals.

 

I got this one https://www.autohausaz.com/pn/AH-2721402401

It included the throttle body gasket. I bought the intake manifold gaskets and injector o-rings separately.

 

I followed much (all?) the advice here and I am back. This is nuts. I don't know what to do next!

Thank you to each of you that responded! Here's what I have done with your advice:

@S-Prihadi I checked continuity to the coil pack plugs. For each one, the line to the ECU has continuity and the three others have continuity to the adjacent connector. The ground connection at each valve cover is clean and tight.
I removed, tested, cleaned, and reinstalled the injectors. Their electrical connections appear to be fine.
I cleared the codes prior to this last startup.
I replaced the spark plugs about a year ago. I didn't touch them as part of this work. It was running fine before the manifold replacement. I'm going to pull these spark plugs to see if anything is wrong with them.

@Raj1471 I pulled out and tested each injector. I cleaned them out with throttle body cleaner. They all sprayed the same. I used new upper and lower seals.
@CaliBenzDriver I replaced all the coil packs. All six are new.
@ygmn I removed and reinstalled the intake manifold. I don't see/hear any leaks.
@JCM_MB I reinstalled the manifold with new gaskets. The previous gasket was aligned and looked fine. I torqued the manifold down to 80nm in a criss-cross pattern. The two vacuum lines on the front are connected.

From my other post https://mbworld.org/forums/e-class-w...will-work.html
@JettaRed I bought the tester you recommended. All the injectors operate fine.
@trigital I removed the intake manifold and the gaskets were fine. I bought new ones for the reinstallation.

Here are my codes again:
ECM codes
0629 Combustion misfiring has been detected.
0633 Combustion misfiring of cylinder 1 has been detected.
0637 Combustion misfiring of cylinder 4 has been detected.

OBD2 codes
P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0304 Cylinder 4 Misfire Detected

My troubleshooting summary:

• All new coil packs
• Tested all injectors, reinstalled with new seals
• Removed the manifold, previous gaskets were aligned. Used new gaskets to reinstall
• Tested continuity at both coil pack connectors

How the trouble progressed:

1. Replaced the intake manifold and found that cylinders one and four were misfiring. I disconnected and reconnected the coil packs and it ran fine.
2. On my way to work the misfires came back. I disconnected and reconnected the coil packs in the parking lot at work and it was fine for the drive home.
3. I parked it for two days and the misfires were back when I started it again. I used a pick to clean out the connectors and it ran fine.
4. I made it to work without any misfire. On my way home I gave it the beans and the misfires came back permanently.
5. Misfires persist after manifold removal/reinstallation,

Next steps? Here are the ideas I have left.

• I'm going to pull the spark plugs from cylinders 1 and 4. If they look okay I will swap them with other cylinders and see if the problem moves with them.
• See if I can find one of those testers that show if you're getting spark. There isn't much slack on that coil pack wire.
• I can get a used wire harness from ebay for $150. That will require removing and reinstalling the intake manifold again.

 

@S-Prihadi Where is that crankshaft hall sensor? Perhaps it was damaged during my work.

 

The one you purchased....half the price of the FCP one....you seriously could have been shipped a bad one.

 

MS! I think you have just identified what make ECU depend so much on decent CAN-C timings.
Thank you!



ECU reads ESP wheel sensors to tune engine combustion

When the solderless Bosch ESP module goes nuts so do the engine timings. Normally these two Bosch VIP computers are supposed to cooperate well but they tank performance under wrap.
👏

 

OP you are focussed on an electric issue... did you read the WIS document researched by Master Surya that says ECU STOPS INJECTING as a protection mechanism for cats.

1. Check fuel trim LTFT numbers
2. Reboot Chassis
3. Clear all chassis faults
4. Check fuel pressure
5. Check fuel trim LTFT again