Has 134000 miles. The guy I bought it from told me he had recently replaced an O2 sensor.

 

It is a timing belt engine, I wonder if the timing belt is a tooth off. With the mileage you have I hope it has been changed along with the water pump. I would want to look at that before doing anything else to it.

 

Like they said above; get the codes and post them. I already had an OBDII scanner when my Aunt's Vue was giving her trouble. I pulled a P0430; which turned out to be a multiple cylinder misfire. I had already bought plugs and coils because I was planning on a full tune up anyways. I changed them out and the check engine light went out; for a day and lit back up. Next time I see my Aunt; I will break out the scanner and see if I get the same code. If so, I will look into replacing the intake gasket. Point is, diagnose the problem before buying parts.

 

Per the above multiple responses and discussion, the codes are already posted.

Interesting you did not get a p0300 for random multiple misfires. Solidifies somewhat Andy's hunch.