Well it first started when I was driving in the rain, the car started hesitating and misfireing the check engine light came on flashed and then went off. It ran fine when it dried out, every time it rained though the same will happen. And now its starting to backfire when I hit the clutch going from gear to gear, and its getting worse every day. Guy at work used to be a diesel mechanic and he said it sounds like a spark plug wire so im going to change them soon. I also have noticed a ticking sound like possibly an exhaust leak from under the hood, that could cause backfire right but what about the rain problem?

 

even though i have a lt1 i had a similar problem it ended out being the oxygen sensor on the right side was shorting out because there was a few cuts in the wires and everytime it rained they kept shorting out and dumping excessive amounts of gas on the whole right side of the motor. have it scannned and see if the o2 sensors are operating in the correct range. just my .02

 

It definitely sounds electrical in nature. I had similar symptoms when the cable that runs from the battery to the starter had touched the headers and melted. The wire was exposed and when it rained the car would buck and backfire like crazy.

 

From Haynes:

1. EGR system not functioning properly
The linear EGR valve feeds small amounts of exhaust gas back into the intake manifold and then into the combustion chamber independent of intake manifold vacuum.
The valve controls exhaust gas flow from the exhaust to the intake manifold through a single orifice with a ECM/PCM controlled pintle. This EGR valve operates similar to the stepper motor type paticular to IAC valves that control idle quality.
If the EGR system will not allow the ECM/PCM to control the position of the EGR valve pintle, it will set a diagnostic trouble code in the OBDII system. This system can be accessed using a special TECH 1 SCAN tool at the local dealer repair and service center.

CHECK
The vehicles that are equipped with the liner EGR valve are equipped with the ODB II system. Special elecxtronic diagnostic equipment is needed to check this valve and should be left to a dealer service department or other qualified repair facility.

2. Ignition timing incorrect
3. Vacuum leak
4. Damaged valve springs or sticking valves
5. Intake air (vacuum leake) leak

 

Wet coil. Early on in the LS1 world I washed my engine without protecting the coils. Car ran ****ty and back fired/ missed for about 3 or 4 days. Then it dried out and has been fine ever since.