Idle - MPG Issue

[Swogman]

:
I have a 98 Explorer 5.0 and when she is started she has a High - Low Idle
Cold Start up Idle is about 1200 RPM and you can watch the RPM tach go up down till she starts to get warm. Then she idles about 650 RPM.

I have replced th IAC sensor since that is what the code came up with but it still does not cold Idle right and she seems to be sucking up gas more than normal. I'm getting abut 11.5 miles to the gallon. I use to get about 15 for combo driving.
No other engine codes and Check Engine Light (CEL) is not on.

Here is what i have done and or changed:
Air and Oil filters
Oil (always change my oil about 3-4000 miles)Sill looks new after 2 months.
Fuel filter
Checked Vacuum Lines. (no leaks found)

I have had people drive behind me and see if they can smell raw gas coming from tail pipe an no gas smell or black smoke.

I'm begining to feel that it is a sensor since the way it idles like a door opening and closing.

Any Ideas folks....?

Swogman

 

[Sams01XplrSprt]

welcome swog

 

[BrooklynBay]

Welcome to this forum! Check for a vacuum leak.