83k miles, recent buy, 1 week old to our garage.

Got a call from DW, while she was out on errands. Slowing down just before pulling into a store parking car starts to shake, she said a left to right and threw a CEL (I surmise bad idle) . After 20 min at the store she starts the car, idle roughness is less then. Drives across to AZ, code is P0302, recommend she pours in a can of seafoam, but did not. Re-starts, CEL is gone and car is back to normal as it had been.

Previous owner upgraded ride and barely drove this this car in the last 3/4 years. They replaced alternator at 60k + serviced tranny at stealer ship, new coil packs some months ago, and engine oil slightly over 1 year ago. When they decided to sell he drove it to work after it had sat for sometime. It threw a CEL, but went away after a day. He thought CEL was resultant from being parked, may be old fuel yada yada.

This being the second instance does it point to something coming undone soon? Second I would like to get ahead of such and get on it now. I am new MB, not to wrenches - I wrench a Camry, a BMW on weekends in my garage UT videos and these forums are handy. That said I have no idea where to start with an MB. Any pointers would be greatly appreciated.

This is all the info I have. I won't get a chance to check it out until tonight or tomorrow.

EDIT
I checked the car a little bit today and starts and sounds normal like it has all week. However, Torque picked up code P0302 and some readiness monitors went incomplete. A week ago torque showed no such codes.

TORQUE TODAY


TORQUE 1 WEEK AGO had no codes so I didn't a screen shot but here is the readiness monitor

 

So have you checked into # 2 cylinder issue. Could be intermittent.