We have a 1999 Mitsubishi gallant , we have a miss fire when ever its raining out ? what could be causing this to happen

If you have spark, but no fire, then check injector for proper activation. If good, check compression. If injector good, and compression bad, possible head gasket, valve, piston, etc.

if the car was driven in the rain the fender splah guards are missing if it was not driven you have old plug wires or on other systems bad spark plug boots that are leaking + to- and the moisture in the air causes this to happen more because the spark is jumping instead of firing the plugs so you just keep cranking the engine but it won't turn over then after it dries out the car will start up but the engine might shake a little or run rough

head gasket is blown most likely

replace the ignition coil. if you want to go all out you should also replace the spark plugs and spark plug wires.

depending on what motor is in your Jimmy and if it still has a distributor, that is where i would start. moisture will get in side the distributor and cause a miss fire. This is a common problem with GM trucks that still have distributors instead of coil packs. Try haveing some one replace the cap and rotor or silicone around the cap and see if it seals.

ok....when you talk about firing, do you mean that only the number 1 cylinder is receiving a spark from the distributor, as with this model, the "timing of the spark and operation of the spark is purely in the distributor, so unless you are 100 % sure that the distributor you replaced is good....i would be loooking at possible engine ecu......(there is no crankshaft position sensors or cam sensors in this model)

However, if you have only found that "firing" means the cylinder 1 is the only one attempting to fire, such as good spark, at the right time, with fuel and good compression, i would be doing a compression check, and double check the timing of the distributor.......

replace also the spark plugs and see what happen if still miss firing change the spark solenoids

check or relace your coil pack due to the fact that when a coil pack is going bad it usually looses its umph. when it get hot and that would explain random miss fires

Usually a telltale of ignition problems. Usually the spark plug wires insulation is gone bad and humidity causes the spark to jump before the plug and thus, prevents the plug from firing. If the wires are OK, then probably the ignition coil's casing is cracked or open somewhere. If the coil(s) is fine (on some engines there is more than one ignition coil), also check the distributor for cracks on its body or cap, and open it up to check the condition of the water seals inside the distributor unit. Should be one of the 3 problems mentionned above, if not, get it checked by the dealer cause it will be some weird problem with the onboard computer or some of the sensors on the engine.

could be a wire crossed, or it's out of time. since you used motorcraft plugs, did you set them properly to the correct gap? replacing plugs without gapping them can cause the sluggishness, out of time can cause the mis-fires and rough running.