Sometimes when I start the truck if I gas or let off the gas at the wrong time it sputters out. After this it has a hard time starting, I have to feather the throttle a little to get it up and running but it takes a few times. This last time it happened it wouldn't start and and gray smoke was coming out the pipe.

Changed six months ago
-Plugs/wires

Changed 1 week ago
-I took out the chip that I bought about 10yrs ago and the truck ran fine, better in fact.

Everything was running fine for the last week don't know what happened. Any help is appreciated, thanks.

 

Hve you taken off the throttle body and cleaned it out real good? Had the problem with a Honda Accord and a 98 350 engine. A can of carb cleaner and we were good to go