Topic: Backfiring and sputtering

[90stangconv]

I recently bought a 90 5.0 mustang conv, the cars has been sitting since 2006. The guy i bought it off of said it had close to a full tank and that he went and filled it. I drove the car for a day and the following day replaced the spark plugs. The num 4 cylinder was the only one that  was partially burned and minor amount of oil on it. did a oil change also and afterwards the car drove fine. Turned it off drove it a hour later and it didnt want to go when i applied the gas and it would backfire and sputter. Took it home checked the plug and they werent gapped right so i replaced the plugs again and its a lil worse and wont stay running. i heard it could be the gas, what else could it be?

[Soaring]

If that gas has been in that tank since 2006, then it could very well be bad gas.  I think I would drain the tank and put in a fresh tank full.  I had my 65 stored for two years one time, and even though I stored it with a full tank and "Stabil" whenever I got back home and drove it about 20 miles, it spit and sputtered on me until I changed out the gas.  It was probably not only bad gas that had turned to varnish, there was most likely condensation that had built up in the tank.
That's the route I would take.  If that doesn't cure it, then you will need to check with spark issues.  But, I'll bet you a dollar to a hole in a donut that the bad gas is your issue. 

[zebo87]

Is it mass air. If so clean the sensor