What can be the problem

 

First off I would guess the O2 sensor or dirt injectors. If not that maybe a vacuum leak somewhere. If its dirty injectors, put some SeaFoam in the gas and see if that helps. BTW, how many miles does the car have?

 

I see this is your first post, so [sm=welcomesign.gif].

It can be your fuel injectors or possibly your upstream O2 sensor. Go down to Autozone and have them scan it for the "P" code to narrow it down for you.

 

This is my first post. The car has 170,000 miles on it. I bought it new and have done all the work to it myself. I replaced the head gasket at 118,000. I have been getting the EGR insufficient flow code and replaced the egr valve. The Check engine light came on and off for a while and now has been off for a month or so. The injectors have never been cleaned except for adding fuel injector cleaner to the gas. Mympg has drop to 27 or so and I am usualy got 32.