2001 Buick Century engine operation

How many tanks of gas has this occurred over, and have you used different filling stations? My theory is that after the vehicle sits, the fuel may have some moisture in it that collects near the pickup. After driving the fuel has sloshed and made the water molecules smaller, and the engine can process it with little or no noticeable symptom. If you haven't changed fuel, I would try it. Another possibility is to determine how old the fuel filter is, and if needed, service it.

Hi Guys;
I investigated your suggestions and replaced the fuel filter. You asked how many tanks of gas I have put in since the problem started, my guess would be 8 or 9 tank refills as this problem started about 3000 miles ago. The refills were at many stations between here in Florida and Mooresville, NC. The garage mechanic checked the pressure drop across the Catalytic convertor and found it accessive so he removed it and found honeycomb filter was all in pieces on the outlet end of the convertor but was fine (in one piece) on the inlet end. Temperarily the mechanic welded in a straight pipe until we can solve the original problem. I wonder if this engine problem relates to the age old problem of condensation in the engine spark distribution system, like moisture accumulation in the distributor cap. Of course this engine doesn't have a distributor cap but maybe moisture accumulates elsewhere in the spark distribution system when the car sits overnight. Do you think this could be the problem?
Thanks for answering my original question and perhaps you can continue to shed some light on my problem. While I'm at it I would like to ask another question. Seeing as how I now have to replace the Catalytic Convertor do you think it would be ok to weld in a new generic good quality convertor like an Eastern Catalytic convertor to save some money over replaceing the whole convertor with pipes to the bolt in connections?
I will be looking forward to your answers an suggestions.
Sincerely'
Stan Ring

There really is no area for moisture to accumulate, other than the spark plug connections perhaps. On the converter, you can go with an aftermarket one, that will keep costs down. In my experience, you won't get the service life out of an aftermarket that you would an O.E. I have seen alot of aftermarket cats go about 2-3 years or so, before they start causing emissions test failures due to high readings. I am not saying it will degrade and clog the exhaust system, I am speaking of emissions and it's ability to oxidize HC and CO. If I had to take a guess, the way they keep the costs down on the aftermarket, is by using less of the expensive precious metals that go into one.