I found a quick fix for a DTC P0303 (misfire) code on a 2002 Honda Civic LX (D17A1) with 200k miles! :-)

The car had a rough idle, hard starting & poor gas mileage. Then, a DTC P0303 code set (misfire cyl #3) and the MIL light came on. The misfire eventually got so bad the MIL light started FLASHING (cat converter destruction in-process)!
I had recently installed 4 CHEAP "remanufactured" fuel injectors from eBay (GTH Motors).

I first tried moving the ignition coil (per the Honda manual), to see if the DTC code would follow. I cleared the code, ran the engine and got the same code (P0303) set within a few minutes, so I concluded that the ignition coil was not causing the misfire.

I then moved the fuel injector from cylinder 3 position to the cylinder 2 position, cleared the code, and ran the engine and had a code set for misfire on the #2 (P0302)! :-)

I then replaced the bad injector and VICTORY! The engine now purrs like a kitten again, has more power, better starting, gas mileage back up to 34 MPGs, no more codes or MIL lights.
MISSION ACCOMPLISHED. :-)

LESSONS LEARNED: (1) Rough idle, hard starting & poor gas mileage problems can be caused by misfire from worn out/clogged fuel injectors. (2) You must be very careful with quality when buying cheap "remanufactured" fuel injectors on eBay.

 

thank you for the input. good lesson to know. kudo's for good trouble shooting.