I have a 1998 F150 with the 4.6L. The check engine light came on and I pulled the code which was p1131,Oxygen Sensor Engine Lean. I have sucessfully fixed an EGR problem but know nothing about what to check to fix this. Any help would be appreciated.

 

Did you try searching out code P1131 using the search button above? I've never had a problem with my O2 sensors but most of the replies I read here usually point to a problem else where. How long ago did you fix the EGR problem? If you had the throttle body off it might not have sealed properly when you put it back together. Or you cracked a vaccum line. Have you cleaned your MAF lately.

 

This code indicates that the passenger side of the engine is running lean for some reason. This is the HO2 sensor mounted on the exhaust manifold.

Since it only affects one side, I suspect a vacuum leak. Check all of the hoses. I've heard quite a few reports of the PCV hose cracking on the 4.6L. You may want to check that first.

Another thing to look at is the A/C condensor dripping onto the O2 sensor. That could set this code also.

Those are the simplest areas to begin.