2007 Honda CR-V automatic stick shift, starts making noise and won't go over 45 mph. This happens when pulling hill then stops after going down hill after a period. Then car runs fine and accelerates property. Car was stored indoors for six months and needs a complete exhaust repair ($1200). Don't want to put in money if this is engine or transmission problem. Fluids are fine , car gets started up every few days, planned to do complete change and flush of fluids. What could be key problem?