Idle acting crazy
I think you guys are on to something.
Somewhere I read that vapor lock can cause a momentary overpressure condition between the fuel pump and carburetor causing the fuel in the line there to be forced into the carb, overwhelming the float needle valve, causing a little flooding. Did I dream that or read that..?
I insulated my fuel lines on my Volare with black foam pluming insulation and zip ties in the pasts, as far back as I could get under my car, about half way back to the tank. That cured my vapor lock issues.
It is strange that if you put your car in neutral the issue clears itself, maybe just the removed load allows the engine to rev up and clear the fuel as well as the the fuel pump can operate more effectively as the revs come up. Does your stock fuel pump have a return line type process? I think those deal with vapor lock better.. I don't now much about fuel systems of these era Mopars as of yet.
One thing to think about when you wrap a solid rubber fuel line around your existing line for insulation.. Solid rubber is a pretty good conductor of heat, a foam or other insulative material (wrap) would yield much more effective in preventing heat conduction to the fuel line. Maybe detach the entire fuel line as far back as you can go, and wrap header wrap around it all!
When I assemble my Duster, I am doing some serious fuel line insulation and wrapping my headers too, that way if I have to work on either, It will take me a year to get at it... hehe..
My two pennies worth..
:)
I have insulated my fuel lines by splitting another fuel line & zip tying it around the ones on the car with the split facing up to allow heat to dissipate. I really do not understand why it clears up in idle, it is weird. It is not like the idle is too low & I have to put it in neutral every time I stop just when I get stuck at a long light. I do not touch the gas pedal at all, just slip it into neutral & the idle slowly starts to recover.