1. Do a cold and warm compression test. You are looking for a bad valve possibly. Also (2) check your electrical connections back to the PCM/ You are looking for a corroded, bad connection/broken wire/ wire rubbing metal. (3) check your fuel pressure. You are looking for very low fuel pressure/ bad electrical connection/ground. Look closely to the areas where the wire joins the loom in all cases.
Since you change a spark plug and it runs great for a couple of days pull the coil and visually inspect it closely for obvious damage. You can test it with a VOM. Also the connections to it for damage. Obvious ? Simply replace it with a good one. Next is the injector and its connections. This is probably electrical in nature, I have heard of front crankshaft problems but the timing there is usually perty catastrophic damage to the pulley.
Last edited by papa tiger; 09-06-2012 at 11:27 PM.