So, my GTA has been misfiring when its humid outside, I noticed that a plug wire was burned slightly and exposed, I thought that it would be the issue, so I changed all the plug wires and while i was at it i changed the plugs, that day i started it up and it ran fine, jump foward a couple weeks and its doing it again. Its most noticeable when you lay into the throttle, any help in diagnosing the problem would be great.

 

Cap and rotor? They don't like moisture inside them.

GD

 

Replaced them a year ago.

 

Brand of components? Did you use dielectric grease? Have you burned a wire again?

GD

 

All Acdelco, i used dielectric grease on all the wires. Ill check for a burned wire in the morning but I doubt it, i spent 30 minutes routing the new wires to make sure they didn't touch anything.

 

Could also be on the fueling side... possibly one injector going bad.

 

Possibly, the car did sit for awhile. Im going to replace the filter this coming weekend, car sat for 10ish years and we replaced the filter once back in 2014. Hopefully its that, if not then injectors is my next thing. Any way to test them without removal?

 

Ohm Test.

 

A hot/cold resistance test is one check which can reveal a failing solenoid, and Multec injectors are prone to that. However, it doesn't provide any information about clogging, sticking pintles, poor spray pattern, or other injector flow problems.

Given the intermittent nature of the symptom, linked to high humidity, I'd thoroughly check the ignition system first. Don't overlook the coil.

 

Never thought of checking the coil, didn't think it could be a suspect. When i can ill get one and swap it out to test. And it idles funny too when humid.