Hyundai Repair: 1997 hyundai elantra running rough seems to be rain related, hyundai elantra, cam shaft

Question
My sons Hyundai started running rough after getting fuel while it was raining.  I checked the wires they seemed very good with no drying, nicks, cracks etc.,  They felt new.  So I replaced the plugs.  He had driven the car to my house 32 miles with no problem.  But the day before after he had sprayed the entire ignition system with an electrical wire dryer after the day before that it wouldn't start or I should say ran very rough sputtering etc.,  His mother sent the car out to a mechanic and I did speak to him and he eventually billed his mother over $300 for replacing an injector.  My son drove the car for a few days and it started all over again.  It reappeared after raining overnight and during the day.  I suspect that this is a fuel problem.  I actually thought he may have got water in his tank the day he got fuel.  But he has since put in fuel a few times.  Never filling it up.  Could the cam shaft positioning sensor be intermittent, could it be a fuel pump?

Answer
First, if your check engine lamp is coming on, check your diagnostic trouble codes and report them back here.  Following the diagnostics for the trouble code typically results in speedier and more accurate diagnosis, since you're checking whatever it was the ECM saw that was abnormal.

If the problem is rain related, I'd recommend checking into your ignition system some more.  Moisture in the air makes it easier for arcing to occur in areas where it's undesireable, causing a misfire.  In most cases, this would cause a P030x code to set where x represents the misfiring cylinder number.  P0300 indicates multiple or random misfires.

Remove each plug wire off the plug and just set it back on, not clipping it back onto the plug.  Then start the car.  Then, one by one (or just the wire in question if you know which cylinder is misfiring), gradually lift each wire away from the plug.  Spark should come out the end of the boot until you get too far away for the spark to bridge the gap.  If the spark comes out of the coil, you have problem with the coil.  If it comes out of the side of the wire or wire boot, you have a problem with the wire.