Mercury

I have a 1999 mecury mountaineer with a code of 401(insufficient egr flow). i have changed out the egr valve and the solenoid(has two vacuum lines and electrical plug connected to it.) and the egr tube(runs from the egr valve to bloke ifold).still problem persists. when i replaced the battery the check engine light went out and stayed off for two weeks, then came back on. my mpg is down to 10 miles per gallon and gas is not cheap. help.

Most likely the problem is in the throttle body passageways to the egr . if you can do this yourself it can be a $ saver. remove the t/body and gasket. be careful of the gasket as it can rip. look for carbon build up behind the t/body. use a small screwdriver and rag with some carb cleaner to remove the carbon, it may also be on the body. do not soak the throttle body in carb cleaner, you will ruin it. only use spray cleaner. also your mileage can be affected by other items, ie fuel filter, air filter, driving habits, quality of fuel etc. nice luck.