99 Audi A6 won't crank

Little while ago I changed the oil pan in my
2.8L AWD 99 Audi A6 Quattro because it
got cracked ran it a bit with little oil and
tried to start it without oil wouldn't start
and realized it didnt sound right. While I
was changing the oil pan I noticed a bit of
what seemed to be a bit of sand?? I just
recently bought this vehicle used so no
idea how long that's been in there but I
cleaned it out best I could, the battery died
I boosted it and it turned over but didn't
sound the best while trying to turn over at
first but held gas down for bout 20
seconds and started sounded fine got out
and it died started up again quick revved it
up a bit as soon as I let off the gas it died
again and Then it would crank but not want
to turn over and eventually just started
making fast repeated clicking noise Let it
sit for a couple days and it cranked a
couple times slowly and started clicking
again let it sit for a month thought I'd try
again and now all I get is the fast repeated
clicking noise coming from engine
compartment no crank at all. Hooked up a
code reader and got misfire from cylinders
4 and 3, random/multiple cylinder misfire
detected, and secondary air injection
system incorrect flow detected. Don't see
why those codes would prevent from
cranking. Anyone have any ideas what the
problem might be?