It's a 98 civic with a 1.5l gasoline engine, automatic transmission,
I had my ignition coil block changed a few months ago after it broke down, and started having issues on damp weathers a few weeks later.
I also noticed a loose screw from the distributor gap (fixed that, tightened it up again), changed all spark plugs to new ones.
I'm absolutely certain that it has to do with damp, moist weathers, since that's the only time it won't start. And yet, when the engine is warm and it starts to rain, then it has no problem starting.
When I hit the ignition, the engine cranks without any troubling noises, the fuel pump also works because I can smell fuel afterwards, the gear is in parking mode, but it sometimes won't start.
And when it won't start, it sometimes sort of misfires (like a promising single combustion stroke, but still won't start).
And when it runs, it runs perfectly, even if it starts to rain on the way.

I'm suspecting it has something to do with the distributor with the spark not getting through because of the moisture getting to the wires somewhere.

Any ideas?

 

Put some plain water in a spray bottle. Start the engine and mist water all over the wires and distributor. If it does misfire and stall when wet, replace the wires and / or cap. If water on the high voltage parts doesn't make it misfire or stall, consider other causes.

One common cause for cranks but won't start, but not all the time, is bad capacitors in the ECU. Normally when you turn the key on but don't crank the check engine light should come on then go out. If it comes on and stays on (or it doesn't come on at all, which could also be a bad bulb), there is a problem with the ECU getting power or ground, or a problem with the ECU itself.

 

Thanks for the reply,

I tried spraying water on distributor related parts while the engine was working but that didn't do anything to the engine.

 

Does it crank when its damp out?

 

yes, it does.

 

Check to see if you're getting spark, check to see if your fuel injectors are firing.

 

I checked each ignition wire for spark. All of them worked, but I noticed that I get visible spark from the distributor as well..
At first I thought it's coming from the #4 ignition wire, since its close to that but I captured an image off a clip I made and it seems as if it's not coming from the wire connected to the distributor, but sort of from the cap's outer area. Weird.
Though, the spark seemed the weakest at #4 cylinder's ignition wire.



Could also be a cracked cap or ignition wire I suppose?

 

Yeah or the wire right above that one has a huge crack in the wire where it goes into the boot

 

Wait until it’s dark and go mist the distributor and spark plug wires with water. You’ll be able to tell exactly where the spark is jumping from.

 

If your CEL goes out after turning the key to the on position, then your ECU is probably functional. If it stays on, then it is either not grounded properly or could have some internal capacitor issues. Check for proper engine ground wire to frame, and also check for proper tranny ground to frame. I had a similar issue last year, where my civic would not start when it rained good. I actually went to AutoZone and bought a new 6ga ground wire and ran it from one of my distributor mounting bolts to the shock tower near the battery for extra ground. I discovered the factory ground wire near the thermostat housing was a little corroded as well as the one from the valve cover to frame. I cleaned them all up and made sure they were within specs with a cheap meter. This was after I had my ECU recapped. All is well now, no more issues.

 

Thanks for all the answers.
I replaced the distributor cap and rotor with new parts and that seemed to fix the issue.
The contacts on both parts seemed to have worn out.