Zksdad,

 First question - are you sure this is a Series II 3800? Reason I
ask: both Series I and Series II 3800s where used in 1995. Check the
8th character of the VIN number - if it is an "L" it is a Series I:;
if it is a "K", it is a Series II.

 If the present engine is an "L" code that 1991 engine should be
useable, but check that cars's engine code to see if it is an "L" as
well (could be a "C", in which case the swap will NOT work). Even if
the '91 engine is a "L" code engine, you will need to swap a number of
parts from the '95  to the '91 engine for it to work right (one
example is the EGR valve and its associated parts)

 If the original engine is a Series II you can't use the 1991 engine
as a swap - won't interface with the electronics in the car (engine
sensors and such). In that regard "willyconchilly"'s advice is
incorrect. While there are similarities between all the Buick 90
degree V-6s going back to the 60s swapping between the various
versions is nearly impossible because of the differences in the engine
electronics, fuel systems and such (plus issues with smog laws in some
states).

I'd take Shep's advice - I agree with him that it sound like you've
slipped time on the camshaft. If that is a Series I engine and you
have gotten 176K out of the original timing gears/chain, that damn
near has to be a record! Could also be a defective crankshaft sensor -
did the Check Engine light come on during that last drive?

 Give us some more details on what happened, like did the missing
happen all of a sudden while driving, did it happen on a restart after
stopping for gas or ??

Regards,
 Bill Bowen
 Sacramento, CA

The other night my olds with a 3800 series II with 176000 miles started
missing(skipping)  badly, no metal to metal noises or overheating.  I was
almost home and so decided to continue on since I figured it was time again
for plugs and wires.    I later tried to start it and the starter would not
turn the engine.  After having had multiple things go wrong at the same time
on cars in the past I thought to remove the starter and have it checked,
nothing wrong with it or the battery.  Since then I have tried to start it
repeatedly and have gotten the starter to turn the engine, although slowly
and with the sound of soft backfiring.  So tell me, does this sound like a
timing issue or what?  If so, how much damage am I looking at.  Would it be
cheaper to replace the engine with another used engine.  I have found an
entire drivable parts car that is a '91 Eighty eight.  
Would that 3800 work in my car, if so, what trade offs and adaptions am I
looking at.  I really like my car, and I do not like anything out there
enough to spend what the price tags asks.  I drive rentals all the time with
my job and I have yet to drive anything in the last 5 years I would consider
making payments on.