1995 olds silouette van 3.8l 3800 about 160000 had had 2 extended periods of sitting when my niece came to me with the problem it acted like a clogged catilac converter maybe low feul presher
after filling the tank with gass i added a can of seafoam ( fuel system cleaner) have driven the van about 24 miles and the speed did increace from 40 to 55 and seemed to idle a little better al at once it got a loud knocking the knock did go away at about 2000 rpm is it possable for the computer to be causing preignition or am i just dreaming and in all reality its really a rod bearing

Make, model, and engine size would help please.

When is the last time this vehicle has had a tune-up ?
If the sea-foam improved the performance, check your plugs to see if they are carboning up.
If you had a rod bearing going out the knock would increase with engine rpm and would not just go away.
Sorry for the late reply had the grand kids this week end.

less than 10,000 miles ago the van would not start and was sent to a shop they were suposed to put in new plugs not sure what else

On a normal tune-up the shop should have done plugs, wires, cap, rotor, ( if applicable), air & fuel filter, & compression test. How is the van running now ? You said it did start picking up speed. Is it still maintaining a decent speed ? Or is it still slow to acellerate ? Loss of power and slow to pick up speed could be catalytic converters.

Just some avenues to explore.

with the pedal to the floor max speed was 55 mph and took a bit to get there
afraid to run it any more at the minute would hate to brake something the knock is loud debating on throwing in rod bearings befor i even start it agin its that bad
dont have much money bearings only about $30 i hate to do it that way
BUT GOTTA STOP THE KNOCK BEFOR I BREAK THE BLOCK