Strange intermittent misfire
Initially, I was thinking this might be the fuel system problem, maybe the fuel injectors are clogged up, so I got a mechanic to do a fuel treatment. However the fuel treatment messed up the fuel pump, so I have to replace the fuel pump and the fuel filter right away. I also replaced the battery by thinking maybe the battery is getting old and not able to generates enough voltage for the spark plugs. But problems continues. It almost happens exclusively when I left my car without driving it for 1-2 weeks. The engine code disappeared spontaneously after everything is back to normal.
Yesterday, the engine shaking and loss of power happened again. I then got an OBD reader to read the code. The code show misfire in cylinder 1,2,3,4,5,6.so today I talked to my mechanic, my mechanic suggest it might be the coil pack which is failing. I looked over on the Internet, I saw there's different answers. Some were mentioning worn spark plugs, clogged catalytic converter, bad Coil packs, oxygen sensor, wiring harness. My mechanic says he can do a diagnostic test, but he might not be able to catch the problem.
So I came here guys, what do you guys think? My thought process would be, if the coil packs are failing, it should cause one cylinder misfire instead of six. Also a misfire should happen mostly during driving rather than just starting the car. The car drives smooth otherwise. If I drive the car every day, there's no such problems. It only intermittently happens(5 times in past 2 years) when the car is left un-driven over 7 days or so. I'm thinking driving the car for 15 mins might drain an uncharged battery to make it insufficient for spark plugs, or when I parked the car first time something might got heat up by the engine on the passenger side to prevent proper firing for the right cool pack. I don't feel comfortable to replace the expensive coil pack without finding a real problem.
Please give me some advice, thank you so much guys.
Dan
Both does cause multiple cylinder misfire so half the engine goes dead not just one cylinder
Autozone and oreilly offer lifetime warranty on coil pack if you buy through them and it's the same part
Even MB dealers will "rewire" left and right ignition parts to diagnose. before ordering and changing expensive parts.

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It seems to happen after I drive it real hard and don't give it a chance to relax before I turn it off. Both of them did it from the time of purchase. I put about 15k miles on each of them.
The problem would always go away after turning the car off and back on. Usually the check engine will stay on until the car is driven 3 times. Knock on wood, hopefully it's not coil packs. =X
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If you're slightly mechanically inclined, it shouldn't be too difficult for you to do yourself and save the extra labor cost as well.

So the Import Direct Ignition is the OEM one ? Just want to confirm because I don't want to get some aftermarket one that I will not trust and the difference is only for $200 !!

I had one that consistently misfired on acceleration cyl # 12 (hardest to get to), the coil had fired straight to the plug side tube and burnt a hole thru the silicone.
Replaced it and never had a misfire again.

I have a 2005 S600 and experience the same issue with OP, finally I purchase the left coil pack (All the code are for left coil ) from Mercedes ( $1050 shipped) and install it last month. So far no issue or problem on start up anymore !!! Now I am ready for some power upgrade !






