My '00 Silverado has developed a miss in humid or wet weather when in 2nd, 3rd or 4th gear above 2000 rpm. This just started and I was wondering if anyone has experienced this problem. The truck has a 4.3 V-6 with a 5 speed manual transmission. It is a C-1500 SWB regular cab 4x2 with 150,000 miles on it. The truck runs fine in clear/dry weather.

 

Have you tried checking the timing or swapping out the distributor cap and rotor ? It's quite possible that they are starting to wear....

 

My 1985 gmc sirra runs very bad to the point of stalling at cruising speed only with parking or headlights are on and mostly when it is wet outside. I have changed out o2 sensor distributor sensor and fule pump but still runs bad. I believe its all tied into the ignition or light switch still serching

 

do you happen to hear a loud squeal when this happens? could be belt slipping.

 

No such noise. I recently purchased a distributor cap, rotor, plug wires and plugs but haven't installed them yet.