When my 1995 taurus lx 3.8L warms up and i turn on a/c the oil light flickers and temp rises.......I turn off a/c and oil light goes out. I had a/c serviced, recharged, the whole package.......plus they put on a new fan blower.......long story short, had oil pressure check done........results,when engine warms up..oil pressure drops to 4 to6 psi, with car in drive pressure drops to 2 to 4 psi, engine knocks on accel when hot...... please advise, what should I tell the repair shop to check out and fix.....I am NOT a mechanic...thanks in advance for any info.