Rep Power: 0

02 civic with 197k. The car will start and run fine for a week, then it will crank but not start. If i wait 60 seconds and try again, then it may or may not start.

I hear the fuel pump humming when I turn to position 2.

No CEL

all i have is the gray valet key - could this have anything to do with the immobilizer?

I had the charging system tested and battery/alternator test fine.

It happens even if the car has been running for 30 minutes and then off for 30

I will replace the plugs tomorrow, but wondering what else I can do before bringing it into the shop?

 
Rep Power: 209

Could be a weak fuel pressure? If, you don't know when the fuel filter was last replaced then start by changing that. If, problem still persist it may be a weak or failing fuel pump that has intermittent proper/improper pressure.

Clean throttle body.