Having issues with a 2013 s550 with the 4.6 biturbo. Took it to benz and they said low compression in cylinder 5 but did test and leak down and engine is fine. What is does is it drives 100% but few times it will put engine light on and it will flash for few seconds then stay lit. And run like ****. But if you park it and come back like hour later it will run for day's even 2 weeks just fine. Then boom back to junk. Now anyone knows a bad cylinder is bad all the time. But what I have done is scanned it and found p0305 and that is the only code! Did new plugs and even new coil pack.when I pulled that plug it was black on half the plug. It was wierd. Then was great for 3-4 weeks. Pulled plug again and it was clean. So ran car with covers off and guess what u can feel all injectors pulspulsing cause direct injection but u feel number 5 and nothing pulsing when light is on. When it runs right it's a pulsing. Like I said Mercedes Benz says it's a bent valve and wants 8k to do a head. But after 947$ for diagnostic no answers as to my question. Y is it turning off the injector. Cause if it's running it runs perfect. Just looking for any help cause Mercedes Benz dropped the ball on this one. Was thinking to send ecu to renntech and do flash cause maybe something in programming is wrong.And no the car is 100% stock just tthinking tune cause they would put new maps in and dought and holes or anything in their programming. Need some feed back and ideas. And yes injector was changed and that had the adaption done by Mercedes. Car has 67k miles and when it runs 100% I mean it's 100% till random light and p0305 is only code even with star tool. Help me please.

 

The engine control module will shut the fuel injector off in the offending cylinder anytime it detects "catalyst damaging" misfire. This is done to prevent damage to the catalytic converters and is normal operation under the circumstances. This type of acute misfire can be caused by several components, as you have mentioned, ignition coil, spark plug, fuel injector, engine compression, and other anomalies, and sometimes new parts can have issues, but rarely. If there was a bent valve, the compression test would show something, if the test was performed at the time the engine was truly misfiring. A bent valve could stop rotating and start to wear the seat inconcentric, then it could suddenly rotate out of the sweet spot and cause intermittent low compression but this is a very rare condition and this condition can be detected with careful, valve cover off, inspection and testing. What seems to cause the misfiring to begin? Does it have to be driven a certain amount of time to get hot, or will it misfire on a cold start? Will it start to do it at idle in traffic or does it have to exceed a certain RPM? Has the dealer verified your complaint, or does the car run fine every time you take it in?

 

Okay it does it when it feels like it, could be just driving or sitting in traffic or right when you start it. Temperature does not matter was more in winter but still came and went. I could drive it on highway and perfect then next second it would miss but I get off highway and hit bathroom or fast food place and come out 20 minutes later and perfectly fine for days or week's. It is literally only shutting down the injector. They had it when it missed and tested with cover off and all kinds of bs to charge for and funny thing was it acted dumb for Mercedes Benz and then I told them is injector firing tech said no I said go to lunch mark valves and everything to know position and start it when to come back. 45 ish minutes later car started perfect no miss no nothing and injector is firing. They had it a week and tried to **** it off again and it would run 100%. Then when I called said f this I will just pick it up he put it all back together and boom missing to take it out and I was there and saw flashing light. Then I said bet it's fine sat down had some tea and muffin at dealer. Went out 22 minutes after they parked it in customer pick up and omg 100% perfect for 5 day's and that inclued a 746mile trip both way and nothing. I even had dumb direct injector cleaning spray done. Nothing changed. I can beat it or baby it but it does it when it wants. And when dealer had it it ran fine when hooked up and then while being read it shut injector off before code and then boom shaking. But it shut it down before star tool saw any data that would cause it to shut down!!!??? If code is up and I clear with mac tool reader and cycle key runs perfect cause dam injector is firing. I think catless down pipes and tune so I can beat it like it needs to be. My s600 was dumb like this when I drove it like a high end can then I went to renntech and did alot of stuff and can't drive it without letting the power out. But guess what 100k plus never needs a thing guess this just needs the same. Only thing about car, I git it cheap it was a embassy car. And all this started after a pot hole in Philadelphia. Had cracked plug porcelain on 5 and the black. But all new now..... Mercedes Benz has no answers why injector is shutting down cause nothing's telling it to. But tech said 5 is one of cylinder deactivation cylinders so maybe car is confusing and shutting only 1 cylinder not 2 opposing cylinders to keep it smooth. Idk I want to beat it!!!!

 

The smooth engine running analysis function of the ME_SFI control module is very sophisticated program and sensitive to variations in mechanical and electrical component tolerances. If the engine is mechanically healthy and sound then problem is most likely electrical in nature. Erroneous cylinder fault assignment is possible but rare. Based on the information you have provided I would suggest that the engine control module be reset to first initialization in order to relearn the flywheel sensor and rotor adaptation then re-evaluate by driving until either fault reoccurs or car is found to be fixed. Sometimes when components like ignition coils or injectors are replaced, the ME_SFI module has adapted itself to marginal components and when new parts are installed the ME_SFI sees the difference and still thinks there is a fault. By resetting the module and redapting it with star diagnosis the module starts a new base line for which it can analyze the smooth running of the engine. Please understand that this explanation is simplified but the program algorithims are very complex.

 

I posted all the adaption stuff was done by Mercedes Benz. When coil and plug done and again when injector was changed. And it was good like 2 weeks. This is a random issue but only thing that is a constant is dumb injector is off when on it's perfect. Anyone know a way to have computer check to see if it's an issue in software? Cause I can never tell when it will do it, right now every 2 1/2 weeks but that could be 200 miles or 2400 it does it time based not miles but once it sits 20+ minutes right back to normal. And Mercedes Benz want to change a head guessing it's a valve but they have no proof that it is. Anyone able to check the maps or programming? U can have ecu or whatever I just need it fixed.

 

if you go to an indy, try checking up an used m278 engine on ebay. it cost about $11,000 and ask the indy to do a swap. i would be fustrated too because how far the drive to the dealer is and the low miles u have. i have about 75k miles.

 

Why would I do a swap? I have the 278. Or u mean to do new engine? If that's what you mean I would just trade up, would love a s65. This was my first v8 s class and it will be the last! And dealer not that far about 40 minutes. Just think this is a programming issue.

 

Yeah swap your current engine with an used engine? The cost at the dealership repair seems overprice and a used engine on ebay cost about the same. But u should try to replace the sensor that keeps coming back up. It might work

 

Hey did u ever figure out what this issue was ?