I agree, get those platinum spark plugs out ASAP and replace them with the new Bosch Copper Plus spark plugs ($20), and throw a new coolant temp sensor in as well ($35). The Bosch Platinum spark plugs are junk,
I have tried them in MBs and BMWs and they just don't work. My 300TE was running like crap last summer, to the point where the wife wouldn't drive it anymore, stalling at stop lights, hard warm start and so forth. No check engine light but just generally crummy performance (I could smell
unburnt fuel out of the exhaust)...did those couple things and the car has run like a champ ever since. When I bought the car it had Platinum plugs in it, I really don't like the Bosch Platinum spark plug in engines that don't specify them.....