Hi i am new hear and i am just 17 years old but i am really seeking help. y dad just gave me his 1991 Chevy Silverado but everytime i turn it on it begins to emmit a black/blue smoke from the exhaust. I really do not know what the problem is, my dad believes that it might be a sensor but i do not know. I really need help repairing the truck to continue attending school and my job, however, unfortunatly i do not have a budget to take it to a shop and are really interested in fixing it myself. Thank you to anyone who is willing to provide help.

 

if its has thottle body injection, it can be the o2 sensor going out..

 

another idea you can try is check the timing or see if you can get the codes the computer is sending

 

if it only does it at startup I would think the valve seals are worn and oil is getting past them. Thus the smoking at startup. Does it smoke all the time or only at startup?