Oldsmobile/Buick Repair: Buick Regal Stalling / Acceleration problem, fuel pressure regulator, vacuum line

Question
Hi CajunSC,

I have a 1999 Regal Ls 3800 - Recently the car has been acting like it is "Possessed" - It does not idle correctly - sometimes wanting to die and some times wanting to accelerate like it is set for a race and the light just turned green. -- The Intake manifold was replaced a year ago, Oxygen sensor has been replaced yesterday - the problem started approx 2 weeks ago - my mechanic had repaired a broken wire in the door for power window which was working intermittently - Basically it wants to stall and accelerate whenever it wants - at times it will run great and just when I am starting to think the problem has fixed itself - it comes back - My mechanic can not find the problem - No codes either. So I am stumped - This is my second buick with the same engine - first one was a 1989 - had similar problem - I traded that for the '99 now it has 96,000 miles and same problem - My wife says no more Buicks in the Family - and I am partial to them because of the comfortable Ride. - Can you help me fix this issue please and save Buick's reputation in our family. - Thanks a Million in advance. - Sunil

Answer
Hi
Does it do it just driving down the road? Like going OK at 40 mph, then trying to accelerate, it "falls on its face" or vise versa (maybe running badly, then when accelerating, it zooms)?
IF so I would check the Catalytic converter.
There is also a special policy from GM  for... I THINK ...10 years or 120k miles .. I THINK this is correct for a factory replacement Cat. converter.
You could check with dealership to see IF your vehicle would fall into this catagory for policy.
Have him check the Fuel pressure regulator.. they do leak ocasionally internal into engine.. have him check the Vacuum line to regulator for ANY traces of raw fuel. Put a hand held vac. pump on it see if it leaks fuel.. If there is ANY sign of raw fuel, replace the regulator.
I would also check the MAF sensor on these engines. Have mechanic "wiggle" wires going to MAF sensor. See if it stumbles while idling.
I also would adivce mechanic to check basics, if not already done, fuel pressure, spark, plugs, etc...
Observe the data.... Idle air sensor, MAF, MAP..
See if he has a data recorder you can install in vehicle so when it acts up with you, you can press a button and it saves data for reviewing later.
He'll find it... it may take some time and patience, but if man make it, man can fix it.
Tell family memebers not to be to hard on Buicks.... ALL  brands, makes and models have problems.
Please follow post back, if needed.
I Hope this helps.
Pawl