I may have diagnosed the problem with the 235. I believe it has a virus, and unfortunately it seems to be contagious. My 1960 Volvo now has the same symptoms. I fear the contagion has to do with the careless exchange of essential fluids.
Many of you directed my attention to the fuel system, so when I found rust particles in the fuel filter I decided it was time to treat the gas tank. So I emptied the fuel, it turned out to be holding almost half a tank. Every gas can I could find is now filled. Since the Volvo was running on empty I poured 5 gallons of my Chevy gas into the Volvo. It now exhibits all the same symptoms as my rebuilt 235 has had - poor idling, backfiring on deceleration, stalling.
Believe it or not I am glad to have a diagnoses. I've let gas sit in the tank over a winter many times without problems, this is the first time I am the victim of bad gas.
I am going ahead with the POR 15 treatment. Maybe I'll have a smooth running truck soon. I also hope to burn up as much as possible of the bad gas in the Volvo before refilling.
Karl
