1999 Subaru Legacy -- all of a sudden, engine malfunctioning....
Legacy outback (ltd) engine sounded perfectly fine for months
took on the highway, up to 70 -75 mph, hadn't gone that fast yet
worked fine all the rest of that night
sat in driveway -- in cold weather (20F) that rose to 40 and back to freezing -- for a couple days
after couple days, it starts fine, but after driving 10 minutes, I notice a barely perceptibly stuttering sound with the engine that started to shake the car
got worse as time went on, lower RPMS made it shake much more, higher rpms seemed smoother.
i stopped to check it out, idling made the car shake really bad, engine made a chugging, puttering sound out of the exhaust.
I put a bottle of dry gas in gas tank, in case water in gas tank
I checked oil next day, was low but had some
started car today, cold morning, and car really chugged and shutoff, gave it extra gas and higher RPMS ran smoother, took foot off gas, low RPM idle made engine cut out.
engine has new spark plugs and wires, but this issue seems reminiscent of the spark plug problems I used to have
any advice would be MUCH appreciated! thank you!