Buick Regal cutting off and/or not starting

Hello. I have a 2000 Buick Regal LS (6-cylinder) and it has developed a real bad problem of not starting properly and when it does start, it keeps cutting off. The strange thing is though is that it doesn't
happen everyday. It's very intermittent. I can go one or two days and it will run fine, driving it to work and everything. But the next day, it'll act like it barely wants to turn over and sounds like it's flooded. During this time, the car emits a real dark, grayish smoke (not white like an oil problem). If I give it a lot of gas for like 5-7 minutes, sometimes the engine will return back to normal. Other times, no success. Then, I'll park the car for about 3 days, go back to it and it works fine.
I'm already in the hole $1000.00 after taking it to four different places. I've had a fuel pump/fuel filter put in; a mass air flow sensor replaced; had two diagnostics performed and oil cleaned out of the box where the mapping sensor is located because I was told that could be giving the computer false readings. On my most recent car shop visit, the mechanic recommended that I have the spark plugs/wires changed but he couldn't guarantee that would fix the cutting off problem. Oh yeah, if I do get the Regal to run normally, it might cut off on me while waiting at a stop sign or stoplight or even while driving! It did so while going about 45 and 25 mph respectively. I was also told that I may have an intermittent ignition control module problem or a faulty catalytic converter. Yikes! Plus, the o2 sensor is showing rich all the time. Could I have an electric short somewhere? How do you check for that anyway? Current mileage on the Regal: 126,000+. Any thoughts on how I should proceed would be greatly appreciated. Thanks.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
--

"Justus" < snipped-for-privacy@hotmail.com> wrote in message
news: snipped-for-privacy@h48g2000cwc.googlegroups.com...
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Anybody check for fuel leaking into the fuel pressure regulator vacuum hose., second what engine here? Does it hold fuel pressure when shut off, does it start right up when it stalls, has anyone disconnected the egr for test purposes to see what happens? These things would be done as basic diagnostics for what you describe.

-
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Thanks for the insight. Fuel pressure is fine, but I'll check to see if the egr was ever disconnected during my last diagnostic.
-w
Shep wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.