Hello: Had oil leak repaired at 65k front engine gasket as well as valve..5 mins after I got the car back it idle rough (didn't happen before)..drove right back..20 mins later..was running fine: reason from mech that maybe one of the ignition coil is going bad..anyhow, 3 days later..now same thing.. CEL not on..replaced plugs..been doing a lot of reading..thanks in advance for any help....