'93 sierra spitting through carb

I just inherited a 93 sierra 1599 w/134,000 miles. It spits back through the carb/throttle when accelerating.Is this problem also causing a hard shift. Help before my wife makes me sell it!

Is the check engine light on? Did you have it scanned? That will tell you if it is running rich or lean?

If it is really backfiring, then you need to check EGR valve, cap and rotor and ignition wires.

Is ignition timing set correctly? What is the fuel pressure? How is the compression?

//2000CAYukon

changed rotor,dist. cap,plugs and wires. running better but now i have to get the oil dipstick off of number 3 cylinder spark plug. two knuckleheads somehow placed the tube between the ex.mani. and block and is laying up against the plug ,nice blue spark.

sorry,dipstick on number 4 cylinder shorting it out.