When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
My van was doing the same thing. I kept putting it off until yesterday.....
I first did some reading and seen folks having the same issue and it was the IAC valve. After spending an hour looking for the part that I seen on the internet, I searched the internet for another hour and found out that they changed them and I didnt have one. I then took the throttle body apart and cleaned it. It was so so gummed up. A thick deposit all the way around and it closed the normal gap. Looking at how it is suppose to function, I'm surprised it would stay running at idle at all. A gap in the closed position is needed. I cleaned and cleaned to get it out (oil sticky residue buildup from the oil vapors. crappy design.
Mine is a van and it took forever just to clean the Throttle Body.
Kinda sorta related but my own 2000 E250 with 5.4 had this same gummed up horrendous mess inside the TB---with just over 285K miles it was due for a cleaning anyway. I was getting somewhat persistent P0171 & P0174 code even after changing plugs, renewing the boots and being sure all COP connectors were in good shape. Since the cleaning not a single issue, here's a few photos of the mess before being cleaned:
I'll never let another TB go that long without cleaning it----even on the E-Series its not that difficult to remove from the intake.