Hi…I am a new forum member and just learning to navigate throughthe forum ………….
I recently bought a 2007 750Li with the N62 Motor and with85,000 miles. The prior owner explainedthat while he was driving on the freeway the engine seized-up for some reason (probablycrankshaft or rod bearing?).I thenbought a used replacement engine with 65,000 miles and swapped out the engines.At that time I replaced the battery,oil, oil filter, spark plugs, coolant and fluids.Onfirst start of the replacement engine it started rough and backfired 2-3 times andran rough for 5-10 seconds, but then settled out to idle smooth.Codes showed misfire in cylinders 1 and5.So I installed new spark plugs and replacedthe coils by pulling the coils from the old motor. After that the engine seemed to run well(although still rough at first start up idle with 1-2 backfires).I took the car for a 10 minute test drive andit ran extremely well….strong and smooth.Once home again I turned it off to grab lunch.30 minutes later I started the car again andgot the same old backfiring and rough idle again at start up.Only this time it doesn’t smooth out after5-10 seconds, but keeps running extremely rough with occasional backfire.In the past several days I have done thefollowing:replaced spark plugs, swappedcoils from old motor, swapped all 4 cam sensors from old motor, replaced crankshaftsensor, replaced fuel filter/regulator, swapped Vanos solenoids from old motor,checked fuel pressure.Not sure whatelse I can check or what the problem might be without pulling the intake manifoldand valve covers for a visual inspection.Does anyone have any suggestions??Thank you!!