Truck sputters and backfires after shut down

[Trimmy]

I have an 86 chevy with a 454 in it and the truck today started sputtering after I would turn it off. I shut the truck down pull the key out and the truck sounds like its off then it will start sputtering and every once in a while back fire. it does this for about 15-30 seconds before it actually totally shuts down. What could this be and how can I fix it?

Any help would be really appreciated

[Dave C.]

Sounds like it's dieseling.  May have to close the throttle blades more (lower the idle screw).  If the engine will not idle fast enough after doing this, then you may have to richen the idle circuit.

[Trimmy]

Turns out I had a fuel line leaking right at the carb and it also had a high idle after fixing the all vacuum leaks specially the vacuum line that was cut in half going to the distributor. I had a bad 180 degree thermostat I replaced for the stock 195 thermostat and so far its running better.