I have a 2002 mercury cougar v6 auto trans, and it is having some problems. At idle, the car has trouble maintaining a steady RPM. Sometimes, it will stall at idle. Also, when you press the gas pedal all the way down, the engine will not go over 4800 RPM, it putts and stalls when it gets to this RPM. No engine light is on, and I have checked vacuum hoses that are easily visible, and none appear to be cracked. I have also checked the air filter and air intake which are both clear. Any suggestions?