I cannot figure out any rhyme or reason to the problems my 2000 Honda Civic is having. Every so often (spring, summer, winter) it will decide it doesn't want to start. I crank the key all the way forward and it does this consistant "rumble/shudder" and repeats this until it finally starts. It is turning over. Sometimes it seems to help if I pump the gas pedal. After about 30-45 seconds (sometimes) it slowly shudders to life. My mechanic did a full tune up checking fuel filter, starter, fuel injector, fuel pump, new spark plugs and cannot find anything wrong. Seems to happen if it sits for a day or two without running. It has happened maybe 6 times in the past 2 years.

Any ideas?

 

If the fuel system checks out, I'd start looking at the ignition. Since you said it does this when it's been sitting for a day or two, I'm wondering if you're getting condensation inside the distributor which isn't allowing it to pass current on to the spark plug wires.