Smoker to hot, losing fuel so to speak

[jeffro10]

I have a problem of starting the smoker and it gets over 300 WITH the vent closed.  I use chunks on my smoker but the temp starts to drop (after a while) and adding one chunk seems to get the temp back up to or just over 300.  I mean, my Ribs have turned out fine (I guess it averages out lol)  but wondering if people have issues keeping the temp at a stable time for long periods?

 

[pineywoods]

What kind of smoker?

 

[jeffro10]

BBQ Pro from Sears 

 

[pineywoods]

Offset model?

 

[jeffro10]

Yes, offset model

 

[trickyputt]

Have you put a thermometer at grate level to very the temp or is that the outside gauge number of 300?

 

[pineywoods]

Are you going by the thermometer that is mounted to the smoker?

What are you using for fuel? Charcoal? what kind? wood? what kind?