I have a 97 F150 4X4 with 207,000 miles.

It is missing only when idling and you can hear it out of the passenger side tail pipe (it is also smelling like it's running rich only on that side.) The other side sounds fine. It does not miss while driving down the road. It has started making a noise that sounds like a horn under the hood while driving.

I have replaced the plugs and wires, O2 sensor on passenger side, replaced both coils, replaced PCV valve and cleaned the air idle control valve.

What am I missing??

 

Assuming it's a 4.6? Any OBD2 codes?

Replace the IAC, that's usually what makes that horn sound.

 

It is a 4.6.

It only showed bank1-O2 sensor.

 

What was the exact code NUMBER?