Hi I have a 1993 500SEL. The other day on my way for a drive I noticed the CHECK ENGINE sign on my dash board. I took it in for a service and the mercedes service agent told me that is has to do with the carbon build up in the injector. I am very skeptical about his findings because I asked him how he came up with this conclusion. His response was that the diagnostic test shows this problem.there is no possibleway a diagnostictest can prove this soI took the car home without repairing it, and it seem to run fine.Since then Ihave put over 1000+ miles on the car.The car runs smooth as usual. But one thing that I have been noticing is that the MPG suddenly goesdown to5MPG until I reach 25-40 mPH, and starts to act normal after that. Any help about this problem is greatly appreciated. thanks
--srig

 

Best to get the diagnostic codes scanned and recorded and analyzed. Could be an O2 sensor, a connection somewhere, the ETAs, wiring harness, etc, etc. I chased mine for two years of odd codes and Check Engine and ASR and ABS lights coming on. Eventually issue was a new brake light switch, tighten all electrical connections possible on engine wiring harness, clean MAFs, and most importantly for me, disconnect battery then remove all of the computer modules in sequence and clean every pin connection and re-install.