1992 300E will start but will immediately quit in gear
 

So this car has been sitting for 7+ years, and I've been trying to get it running lately...originally when it first started sitting, my dad told me it was a water pump that needed replacing, but as time went on he said it might need a new wire harness (Cali rodents are ruthless). He passed not too long after that and I'm left here scratching my head on why the car starts and runs but hates being in gear.

I've replaced the water pump, coolant, serpentine belt, oil, and oil filter. Fuel was empty so I put some seafoam and half a tank in, and changed the fuel filter. Fuel pumps are noisy and work hard even after the fuel filter change. Before the fuel filter change couldn't get it to rev past 3k without dying and now it revs to right under 5k and will die. I've put new champion copper spark plugs, single-pronged, gapped at 0.032 (the ones listed in the 89 owner's manual) the ones in the car were 4-pronged platinum spark plugs that were just a little black. New spark plugs didn't change how it ran, now it just starts a little easier. That was done before the fuel filter change though. Now I am guessing sensors are to blame, or even the OVP, but the fuse didn't blow in it either. There was also a cut wire to a plug that went to a connector under the oil filter that I fixed, but now the car burns oil (blueish-purple exhaust smoke). I've looked at some other threads similar to my issues but some don't get resolved or they point to an issue that I fixed. Maybe I missed a thread with issues just like mine and if so can you guys steer me to it? This car does have 203,214 miles so some would say give up but I would rather not. Already put work into it I'm not stopping now.

Also, my dad tried selling this car on the forums a longggg time ago but no one took the chance to snatch it up so I guess he racked up another 93,000 miles on it. This was the thread: http://www.peachparts.com/shopforum/mercedes-benz-cars-sale/382111-92-300e-sale-only-110-000-miles.html