I have a problem. I have a 91 Honda accord (look in signature for specifics) that I recently had the motor replaced. Now when I turn on the heat I smell exhaust fumes. The car is not loud nor do it sound like it has an exhaust leak. Now it does, spudders when shifting gears. It only does that when I am going thru the gears. What bothers me the most is smelling the fumes when the heat is on. I don't smell anything when the heat is off. What could be the problem?

 

improper fresh air piping or excessive exhaust leak, probablt at manifold connection