dentar

Picked up a nonrunning E55 that havnt been driven for about 1 year

Problem: checking fault counter in Icarsoft the engine misfires (acording to ECU, i cant feel any misfires myself) badly under mild throttle
So badly it goes into limp mode after about 20 meters.
Throws codes cyl 2 + 4 + 7 + 8, again i cant feel the misfires at all. During mild throttle it logs misfires between 1500-2500 rpm
If i do full WOT from standstill the car works flawlessly, no misfire logged at all.
same as idling or slowly revving up to ~1500rpm
Behaves the same cold or warm
No cats on it
Car is stock

Things i've done this far:
Fuel pressure steady 75 PSI, no noticable drop during revving and holds pressure after shutdown
Smoketested for vacuum leaks, no leaks,
All new sparkplugs from Mercedes, checked gap, switched them around.
4 new ignition coils, + swapped around
measured Ohm on all ignition wires, ~2.1k ohm on all
swapped around + ultrasonic cleaned injectors
drained tank, fresh gas in it
reset TB + ECU adaptions
great compression on all cylinders, all withing 1-2 PSI of each other
ECU bonedry, no corrosion or anything
swapped o2 sensors with know working pieces
flashed a stock tune to the car for testing purpose, no change (not sure if the car was tuned before)

Since ECU logs 4 cylinders misfiring badly, and i cant even noticing it by feel, i'm starting to think the car isnt actually misfiring, it just "believes" it does so.
Fault counter logs like 40 misfires per each of these cylinders within a couple of seconds..

What is it that logs the misfires? knock sensors? or is there anything else these 4 cylinders have in common?'
no misfires logged whatsoever on the other cylinders.

Im getting low on ideas

austingtir

I would go over it with the smoke tester again its very easy to miss stuff with those smoke testers unless you spend alot of time doing it in multiple place and off every single vacuum and pressure line. I do every vacuum line individually these days due to missing stuff like little cracks in those bends they have going to the SAI valves etc.

Also check the line going back to the charcoal vacuum cannister. That ***** caught me out on a c200 kompressor as I had basically tested everything except for that and soon as I put the smoker on it I see smoke coming out the rear wheel arch. Once I blocked it off my check engine light disapeared and got normal fuel trims again.

Also check the valvecovers are sealed right and any pcv valves functioning correctly. I just had an e55 that was misfiring because of bad valvecover leaks.

dentar

I did eventually find the problem, one i kinda created myself.

I bought the car with a cracked flex plate / flywheel, the one that connects the engine to the transmission. I had that replaced with a used one with same part number, along with new CPS.

After all my diagnosing i eventually came to the conclusion that the engine had exactly everything it needs to run perfect yet it logged misfires, that i couldn't feel or notice myself.

I ended up buying Benzninjas STAR system, deleted the flywheel adaptations and VOILA! the car runs perfectly.

So even though the used flywheel i replaced the old one with was the exact same P/N, the variances where so small that the adaptations had to be relearn.

bbirdwell

Key piece of information you just provided. From my technical files came the following:

Flywheel Adaptation must be performed after replacement:
􀂾Flywheel
􀂾ME-SFI Control Module
􀂾Engine Mounts
􀂾Crankshaft Position Sensor

dentar

I did in fact see that WIS around the same time i started this thread, then again i read so many threads with people replacing engine mounts / CPS without the need of relearning adaptations. There's not much info about cracked flywheels though. No matter how much i tried "wiping" the adaptations with disconnecting ECU, batteries etc i could get it to work. I only had Icarsoft MB 3.0 at the time so i ended up eventually with buying the STAR system as i was almost certain at this point it was the adaptations.

Maby someone can find this thread facing the same problem and get some use of it

nd-photo.nl

Never knew this, I will reset the flywheel adaptations tomorrow as I replaced my engine mounts just yet...Thx again @bbirdwell !

bbirdwell

Attached is the tech document I have on my hard drive. It reflects the flywheel adaptation screens in Xentry.

dentar

On page 7 is exactly where i got stuck trying to DIY this without STAR:
"TIP! Quick procedure for Flywheel Adaptation: Transmission in PARK range, slowly run engine to 2500 RPM for 30 seconds After the above is performed, drive vehicle to complete Flywheel Adaptation"

You MUST delete the old adaptations with STAR before doing this procedure, I tried this procedure multiple times, before i got the star, to no avail.

Nowhere in the WIS does it mention that you have to delete adaptations first before re-learning. However it is necessary, at least for E55