After replacing the spark plugs, wires, distributer cap, rotor, egr valve, and pcv valve and cleaning the upper plenum including egr passage of all carbon build up from 105k miles of driving I have a weird problem. My service engine soon light is flashing when I start the car, however if I put the key in the run position and wait for the light to quit flashing and then start the car their is no problem and it doesn't come back on. I've heard enough times about the flashing meaning a misfire but I don't know why mine would flash with the key just in the on position with the engine not running. Car fires up and runs great with all of the tuneup work. I am going to try and get codes pulled but not sure that will produce anything since neither light is constantly on. Any help or thoughts would be greatly appreciated.

Thanks in advance,

 

What's flashing? Check-Engine lamp or Maintenance Required lamp?
Misfiring would be the Check-Engine lamp.

Maint.Req lamp is ONLY based on miles since it was last reset. It's just a reminder for oil changes every 7500 miles or whatever distance.

Key OFF.
Press & hold the odometer reset button.
Key ON while continuing to hold the reset button.
Continue holding that button for 20 seconds or something like that.
It'll flash a few times then go off. Until 7500 miles it comes back on.