Symptoms of a failing ignition module?

[Smokehouse69]

I have a 94 1500 5.7 it has developed some strange habits lately. I first noticed the tach jumping around, then a couple of days later it started running very rough and missing pretty excessively. It seems to be worse when the engine is cold, and sort of smooths out while cruising at freeway speeds with only an occasional jerk of the tach and engine.

The engine is in good tune, new plugs, wires, egr valve, distributor cap and rotor, TPS and manifold temp sensor. The ECM isn't throwing any codes.

Could this be a symptom of a failing ignition module?

Thanks

[Shaners]

Possible O2 sensor or a cracked plug or bad/loose wire. I know you just replaced the latter two, but I've seen it happen before....

[Import Hater]

I first noticed the tach jumping around,

 

an occasional jerk of the tach and engine

This does sound aot like a module going out. Or could be a pickup coil too. And a faint chance that it could be an ECM.

 

Rob