hi. i hope someone can narrow my efforts down a bit in solving a problem that comes up only when it rains. its a 98 civic with 100 000 miles and the base engine. it used to just run rough -like on 3 cylinders- when it rained hard. i did a tune up with plugs, wires, cap and rotor and had no changes. i don't know what dart to throw next, as there are no engine codes. last night it rained, and today i have the first no start.

thanks for any advice

 

Usually misfire only during wet weather is caused by old spark plug wires. Given the recent tune up, I think you now have a separate problem.

First, turn the key to ON(II) and listen in the rear for whether the fuel pump primes for 2 seconds. If so, next check for spark. Disconnect a plug wire at the plug and insert a spare (good) plug into the end. Ground the threads of the plug against a metallic area of the valve cover, and then have a buddy crank the engine. You should see bright white bluish spark at the tip of the plug (not weak orange spark). Post the results of these tests to obtain more feedback.

 

Did you use OEM wires, or parts store knockoffs? Same thing for the cap. Check the cap for cracks inside and out. Could also be a crack in the coil if the other parts are good. This almost has to be something with the high voltage side of the ignition system.

 

yep. everything checks ok: wires, cap, fuel pump, coil, timing chain. the mechanic i go to told me he doesn't ever remember replacing a coil on a civic, but he did alot of distributors. so i won't be throwing any more darts. we'll see what happens...

 

check anywhere that water could cause a short. Water in the tail lights? Dunno if they did the wiring much different in your year but in my 89 a badly grounded tail light would cause my engine to lose spark.
Check the little stuff before you go swapping expensive parts.
Just poke around with a multimeter.