4.3 Hesitation / Stumble

I’m having a throttle stumble condition in my 1995 K1500 4.3LV6. It will stumble badly off idle on a hot re-start, for the first several minutes then it gets less noticeable but still has a lazy throttle response. On a cold start it just has a slightly lazy response, but not so much a stumble. I have replaced the cap, rotor, wires and plugs, checked the base timing (right at 0°), and measured the coil with an ohmmeter, and it checks OK. The other day while accelerating up a slight hill it did throw a code 42, which is the ignition control circuit. I’m suspecting it’s either the coil or the module, does this sound right?

could be the module but i would do the tune up first.. you dont know the history of the truck so who knows when it was replaced last.. sounds like its loading up and not getting enough spark to fire it off..

Sounds like the ICM. If you have an autozone near by you can pull it off and they will test it for free. Thats what I did when the one in my Suburban went bad.

Tonight I swapped the coil with a known good coil out of another truck, and the stumble was still there. It seems worst after it has sit for over an hour and is re-started. I will try the module out of the other truck to see if that cures the problem, or maybe just have it tested.