Please help - My Smart started misfire 1500km ago with engine misfire on cylinder 1 - replaced all 6 plugs, plugs on cylinder 1 was totally carbonded up the rest was like new. Engine started misfire again, the funny thing this time is when you switch the engine off and start again it runs fine for a few minutes and starts misfire again - thought it was the same, took out the plugs - this time the top plug of cylinder one was burned away, bottom plug had a bit of carbon but was fine. Replaced the plugs. Every time you Start the engine - same thing, runs fine for a few minutes then start misfire and loose power. :shrug::shrug: Can it be the injector?