My 03 Exp had a rough idle, so I checked the codes, said misfire on cylinder 1 and 2 o2 sensor codes. Replaced 2 of the sensors and the plugs, it went off, but came right back on. Replaced the last 2 o2 sensors, and it still rough idles. Reread the codes and it said idle sensor error, and bunch of codes on the o2 sensors. Any ideas?

 

Search "Expedition "Rough Idle" and read my story for 98 Ford Expedition, bigtill43 member. The answer may be a $30.00 part located at the rear of the Intake Manifold, behind the Control Valve. There you will find where the PCV hose connects to the Intake Manifold.There is a rubber elbow that gets hot and brittle and will crack. This crack will cause a vacuum leak. To locate this, start on the passenger side Valve cover. Find the PVC Valve and trace the hose up to the back of the Intake. There you will find the elbow. Replace this entire hose at the dealer. It comes will a NEW PCV Valve attached. Rough Idle fixed with Ford Genuine Part # F75Z-6C324-JA.

 

Alright thanks.

 

My '04 was doing the same thing and showing the same codes. After replacing the two upstream O2 sensors, no change! THen I read your post and bigtill43's suggestion. By doggie that was it!!! The pcv elbow just out of the intake manifold had a hole in it. on the '04 you can replace just that elbow without having to buy the entire assembly. Genuine Ford part is about 18.00. Thanks bigtill43!