Several posts over the past year have dealt with a misfire people have had that has been intermittent, and usually occurs at around 2500 RPM. I had the same thing happen- except the occasional misfire turned into a cylinder that was dead most of the time. The engine lacked power, the CEL kept flashing, gas mileage went to crap, and the computer kept posting a code 306 (#6 cylinder misfire).
I replaced the coil pack, plug wires, and injector on that cylinder, and Seafoamed the engine (again) and cleaned the fuel system and air filter. I had good Bosch platinum plugs, and they tested good in impedance, so I didn't replace the plug.
Well, I was out of ideas, so I replaced the plug. And that was it! The porcelain insulator on the plug was cracked, and sometimes the spark would jump through the crack to the block, grounding the plug and causing a misfire. I know others have had the same problem, so it wouldn't hurt to change those plugs!
I replaced the coil pack, plug wires, and injector on that cylinder, and Seafoamed the engine (again) and cleaned the fuel system and air filter. I had good Bosch platinum plugs, and they tested good in impedance, so I didn't replace the plug.
Well, I was out of ideas, so I replaced the plug. And that was it! The porcelain insulator on the plug was cracked, and sometimes the spark would jump through the crack to the block, grounding the plug and causing a misfire. I know others have had the same problem, so it wouldn't hurt to change those plugs!