Just got a used 2004 2.4L accord ex, 204k KMS on it... (60k mi). Pulled the plugs, they looked original.. had the discoloration at the business end of the ceramic piece and they were looking worn. How long are these NGK IR plugs supposed to last... to me, i think these ones were factory.... and not sure if the air filter wasn't original either...it was pretty dirty.

To add to the problem, the temperature sensor must be gone... after 25 minutes of driving/idling, it was still reading cold on the guage, and the car starts rough from warm start.

would the ECT cause a rough start from warm?

 

The ECT and temp guage sensors are separate sensors. The thermostat probably needs replacing. (wouldn't hurt to check the coolant level in the radiator. If it's really low, could be air in the system causing trouble.)

Honda says the iridium plugs are good for 100,000 miles. I swap mine out every 50,000. I don't want to take the chance that the plugs may seize in the bore after 100k. Stick with OEM NGK or Denso plugs.

 

At Honda in Norway, the sparkplugs in this car is supposed to hold 120.000km.
We change these at 60.000km
They are made of iridium and are really expensive