Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
What fault codes is it storing when its scanned?
Without knowing what fault codes you have stored then it would be stab in the dark.. If it mulitple missfire then they may want to check for vacuum leak or intake leak.. if it timing related as you say or they think it maybe be.. then a decent wiring diagram. pico scope and trace the cam and crank signals and compare witha known good trace..that way they could see if the timing chain is indeed stretched..without having to dismantle the engine or having to manually time it up too see if the timing chain has shifted...