AudiForums.com - pinging noise on startup

1997 A4 B5 model
1.8t with quattro
180,000 km
auto tranny, no tiptronic

here's the history of the problems i've been having

6 weeks ago: oil light comes on while on the highway. took it to mechanic, says the oil pump gave out, replaced it for $400. since then there has been a pinging noise coming from the top of the engine on startup that only lasts about a half a second. mechanic told me this is normal after the oil pump is replaced/after an engine rebuild.

4 weeks ago: temperatures drop to -50 celcius for a week and the car will not start. after cranking for 5 seconds the oil light comes on and starts beeping. when it warmed up for 2 days the car started again, mechanic said there is no problem. take car home and drive it for 1 day. temp drops back down to -50 for another week. car wont start.

2 weeks ago: weather lets up and we've had standard -20 celcius weather. car starts, but pinging noise is still there on startup. after running for 5 minutes the pinging is noticeable again, but not as loud as when the car is started. there is also smoke coming from the passenger side of the engine that is present at startup and then stops after a few minutes (smells like oil).

if you can help me out with any of these problems; pinging noise, not starting in cold, oil smoke from engine, it would be sooo appreciated!! i just bought this car in july and now it hasn't been running since before christmas! this is a DISASTER!