Oldsmobile/Buick Repair: Hesitation, vacuum problem, muffler shops

Question
QUESTION: I have a 2001 Bravada.  When I first start it up and put it in either drive or reverse, There is a major hesitation and what sounds like a backfire coming from under the hood.  It also happens every time I get gas.  It like there is air blowing out of the carburetor. Its like there is no gas  getting to it.  It seems like it may be some kind of vacuum problem.  Also when I am stopped or have just been driving i can hear what sounds like the gas tank under the car kind of expand or pop?  that is what makes me think it is some kind of vacuum problem.  This has been a problem for a while and seems to be getting worse.. There are no lights on on the dash.  No Check Engine light ect.. What could it be??

ANSWER: Hi
I have NEVER heard of any thing like this.
So that being said I would REALLY take it to a repair shop your famililar with and have them check it out.
I would also recommend having it checked quickly in case it is a serious fault.
I Hope this helps
Good luck
Pawl


---------- FOLLOW-UP ----------

QUESTION: Thanks so much for the response,  I was wondering what kind of issues I would have if the car was in need of a major tune-up?  I have had the car for about 4 years and I have never had a tune up.  Could the lack of a tune up and all the checks that are associated with a TU be contributing to the poor performance?

ANSWER: Hi
I will say a tune up will NEVER hurt.
(Plugs,wires, dist cap, dist rotor, fuel filter, air filter).
Just sitting hear, re-reading your original; post, I am just thinking MAYBE your catalytic converter may be internally broke apart, causing performance problems and noises.
MOST muffler shops will preform an exhaust system check for either free or a very reasonable fee. Most will also check the converter same, free or small fee.
You may be able to get it done all at the same location, eg..Meineke or Midas or similar type exhaust shop in your location.
I hope this helps.
Please, follow post back, if needed.
Pawl

---------- FOLLOW-UP ----------

QUESTION: Ok I have had someone who knows about olds listen and look under the hood he says it is my O3 sensor.  the one that is near my air filter.. He disconnected it while the car was running and it cut out immediately... Then he disconnected it after that and the car took a little longer to cut out?  He suggested that I get a new air filter I have not done that yet but I am going to do that.  It seems as though the car is still having the same problem but not as bad the day he disconnected and reconnected..Could the O3 sensor be going bad?  or does it just go bad and not begin to go bad.. Is it either good or bad?? .Does that sound right??

Answer
Hi
I think the O3 sensor located where you state is PROBABALLY the Mass Air Flow Sensor.
The O2 sensore are located in the exhaust system.
It may VERY well be the Mass Air Flow Sensor (MAF).
It took longer to cut out because the computer defaults to "Open Loop" and runs on pre determined control program.
The MAF CAN intermintantly go bad and good bad and good,etc...
I Hope this helps.
Good Luck
Pawl