Crusader engine problem

[MarkMuck]

1992 454. One of two. One fuel tank. Other one runs fine.

Port runs rough at idle. Sometimes if it's running at say 1200 it might jump to 2000 without touching anything. Sometimes it might be running at 1300 but the gauge says 800.

Replaced: plugs , plug wires, carb rebuild, cap and rotor.
Have not touched coil. Possible timing issues?

Help please.

 

[JimPend]

Check timing advance weights for rust.

 

[jtybt15]

I think rusty distributor springs is Jim P's only fix-it cure...even if the coffee maker is on the blink.

Is the engine under load or ideling? The tach thing may be an indicator of a loose or corroded coil connection or ground. The ground circuit from the coil goes from the coil to the dist. If you have TB IV or V, gotta check the trouble shoot from Geo(GVP).

 

[Sandy]

Good advice as always. Mark, you might keep way back in your consideration, it can work the other way around too. A failing tach (shorting internally) can affect ignition, though usually not intermittently.