i have a 91 b2200, and my question is what causes my truck to suck as much gas as it does. It never used to go through gas as much as it does now a couple of months ago. It's a 4-cylinder. I put a new exhaust on the truck thinking that was it, but it had no effect. I only get 110-125 miles on a full tank where i used to get 300 miles for a full tank. Any suggestions on what it could be would be nice.
Thanks

 

#1..Carburetor could be at fault if float level is too high or is overflowing.
#2..The air/fuel solenoid in the carb could also be stuck causing an overly rich condition as this directly controls the fuel mixture.
#3.. The oxygen sensor could be stuck in a lean condition due to internal fault or external vacuum leak. This would also drive the mixture lean as it is the main input to control the air/fuel solenoid.
#4..Coolant thermosensor indicating a cold engine condition to the PCM which would also keep it rich and in open loop fuel control.

 

also, some times when i'm driving my truck will sometimes studder, does it more often when i gas it fast, its manual transmission, but it depends how good i start off, if i start off good in first then it dont studder, if i start off not as good it will studder, makes no sense to me..