See exaust piture - 1991 Honda Accord

https://www.ifixit.com/Answers/View/156364/How+to+do+valve+adjustment

Have the exaust system checked pluged up cat will act like that
The exaust cant get out so thats when it dies once the exaust bleads off it will start again

That should be bank 1, sensor 2, and if installed, that is usually the one just before the cat converter.

excesive "short trips" cause's condinsation to buildup inside the muffler not giving the exaust system a chance to expell or burn off the condensation inside the exaust system take it out on the freeway or a road that will let you go 50MPH or better to get the exaust system a chance to get up to operating tempatures and to push out the water from the muffler and burn off the rest

Bank 1 sensor 1 --- on left side of engine in exaust manifold .
Bank 1 sensor 2----- on exaust system near converter
Bank 2 sensor 1----- on right side of engine in exaust manifold
Bank 2 sensor 2 ----- on exaust manifold near converter

Pollution control,air injection,you could just pinch the small pipes closed with a pair of vice grips and never know the difference.

Well there are several different ways you can install an after market exaust. The two most commom ways are weld in and clamp in. To stay legal most usually you will go with a cat back exaust. It gets its name due to the fact you leave the factory catalitic convertor in place and the rest is all new.

The easiest way to install a cat back exaust is to purchase the model exaust designed to go in you Nissan. These usually use the same bends as the factory. They also use all the same hangers.

1. Using a reciprocating saw, cut the exaust loose about 4 inches behind the converter.

2. remove all hardware from the factory exaust. Anything that will not be used in the reinstall.

3 Snake the exaust over and out from above the rear axle.( If it has one)

4.If any new hangers need to be bolted in, go ahead and take the time to install them now while everything is out of the way.

5. Now you are ready to install the new exaust system. This is ususally reverse of the disassembly given it is a one piece exaust. If it is a multiple piece exaust system it may need to be welded together first or once installed. If it is a clamp style assembly, install the exaust with all clamps in plce, but not tight.

6. once all the components are installed, check everything for alignment. Once you are happy with the fit, you can go ahead and weld/clamp everything in place.

If you are getting exhaust fumes in the engine compartment I advise checking the exhaust manifolds for cracks. When the engine is cold remove the heat shield from the manifold using a 12mm socket and inspect from the top and underneath for any cracking.

hi im wes the o2 sensor is always in the exaust newer buicks have one before the converter (sometimes in the exaust manifold) one after the converter if it has duall exaust it could have four
left bank sensor one is before the converter on drivers side bank two sensor 2 would be passanger side after the converter does this help?

hmm. . . design . . its kind of wierd tho. . . did it come like that brand new? anyway it really doesnt matter. . you see alot of dual mufflers on cars too. .maybe they just wanted the exaust pipes to be smaller. .

instead of installing a huge single exaust they prefered a sleeker tri-exaust. . . doesnt really matter. 8) you know how the japanese are. . hehehehelove to be pioneers