Hyundai Repair: 1999 Hyundai Elantra, hyundai elantra, coil assembly

Question
Car runs great for a few weeks and then right in the middle of a drive the check engine light flashes. Total loss of power pumping the gas to go 20 mph. Engine is knocking and smells like raw gas in exhaust. Twanging noise from engine compartment. Then 20 minutes later its fine again. Codes from my reader P0300, P0302, P0303. Have
replaced the timing belt, the spark plugs, and the plug wires. Also the fuel filter, air filter. With two cylinders 2,3 misfiring, should I replace the coil? Is there a sensor that can cause this? Or should I start looking at the fuel injectors? Or What? Thanks for the help.
Dennis  

Answer
Since you're misfiring on cylinders two and three, the ignition coil is an immediate suspect because one coil pack controls both those cylinders.  

You should also recheck the spark plugs and wires for good measure, however.  Their failures are much more frequent than the coils.  Inexpensive plugs and wires often have problems shortly after installation.  On a visual inspection of the plugs, make sure there are no carbon tracks down the porcelain.

You might also try wiggling the wires in the connector to the coil assembly.  It's possible you have a loose connection or a broken wire that's intermittently making contact.