This can be caused by so many things, especially with this many miles. Have you checked to see if the fuel pump pressure is within the manufacturer's specs? When was the last tune up? Have you checked ignition timing? Have you checked if the catalytic converter is plugging? Have you checked engine compression? Also, have you checked to make sure there are no major vacuum leaks.
One last thing. Is the check engine light on and have codes been reviewed if it is on?
Thursday, September 25th, 2014 AT 6:36 PM