misfire and backfire underhood

I have a 2001 oldsmobile aurora 78,000 miles on original motor. the car misfires , backfires underhood,and excessive gas consumption,also sounds terrible at the rear exhuast. Has anyone had these problems if so i would appreciate some help. thanks. 3.5l motor issue stated after i filled up at
cheap gas station.

Perhaps you answered your own question.
Filled up at cheap gas ...

Maybe you got some water in the fuel..

Siphon out a galllon or so,, let it sit and see if the water seperates from the gas..
Try some dry gas.. or siphon off half a tank and fill w/high test ..
burn it all off and fill again with known high grade gas.

Perhaps you answered your own question.
Filled up at cheap gas ...

Maybe you got some water in the fuel..

Siphon out a galllon or so,, let it sit and see if the water seperates from the gas..
Try some dry gas.. or siphon off half a tank and fill w/high test ..
burn it all off and fill again with known high grade gas.

I will give it a try and see what happens, thanks

Still have the same problem,car has been parked for over a year,taking my time and replacing parts here is a list,cam sensor,complete tune up,fuel filter,pvc valve,o2 sensor,and bought used coils packs. I have the number 5 spark plug that stays wet with gas,the others are fine,was wondering could it be the fuel injector on that plug,fuel pressor sensor,or pump considering I don't have a way to tell the volume of cas in the tank because the hand don't work.I also checked the catalytic converter and it was good. any suggestions...........

Have you checked to see if the injector is leaking fuel? Do you have nylon or steel fuel rail?

you know im interested in whats causing your problem as i am having one of the same if you figure it out could you email me and tell me what it was?

If the car has sat for a year with fuel in the tank with no additive, you can bet the tank is corroded inside which is why your sending unit is no functioning. you may end up dropping the tank and inspect it.

Plug wires were an issue on my 98 Aurora for misfires and backfiring,,,BUY the BEST QUALITY WIRES, may save you down the road!