calys968

My car is backfiring almost every time I shift and it's also getting really crappy gas mileage. Besides that it's running fine, no stalling, sputtering, etc.
Does that sound like a bad O2 sensor?

Gloveperson

iTrader: (9)

That or a fouled plug.

calys968

Sorry if this is a really retarded question but what would a fouled plug look like? Would it be black?

Gloveperson

iTrader: (9)

http://www.dansmc.com/Spark_Plugs/Sp...s_catalog.html

DONAIMIAN

iTrader: (18)

Ive seen it happen on stock cars with OR pipes, but they didnt have bad gas mileage.

01TAFlyer

iTrader: (4)

My car did this one time, it was two misfiring plugs, now the misfires weren't bad enough to throw an ses code, and it seemed to drive fine (kinda sluggish though), but it backfired during every shift at anything past like 25% throttle. So I say to change your plugs, I think that if it was a bad o2, that your drivability would be different.

SlpLS1

iTrader: (1)

if it was a bad o2.. u car would be sluggish and it would kinda jerk back and forth. no power.. and it would throw a code.. after about 10-15 miles

pistolpigg

I read somewhere about bad check valves in the air system piping, might be another thing to check

calys968

Ok, I've noticed that my car is only backfiring when I'm low on gas. And I'm not talking about when it's running on fumes, it does this whenever I get down to the last couple gallons. Should I still check my plugs?

Ru2n00n3er

iTrader: (13)

Might be bad fuel in your tank, and it's just sitting at the bottom of the tank each time you fill up? Maybe try using it all up before you refill the tank next time.