Rough Idle 98 Windstar

Lately I notice when the van is in park or neutral it has a very rough idle. But it doesn't happen all the time. When I'm driving it, it seems fine. The fuel pump was replaced last year so I don't think it's starving for fuel. I also just cleaned the TB last weekend it didn't really help much.

Any ideas??
Thanks,
Anthony

Vaccum leaks, a vaccum leak may show more problem at idle....as vaccum is high.....and the air leaking in is a greater percentage of the air going into the engine at idle.....PCV valve, or line from PCV valve to the top of the upper intake manifold.....the flexible elbow that is on top of the upper intake manifold.....right next to the throttle body....can develop a crack on the inside of the bend.

IAC (Idle Air Control)....

Air Filter

MAF (clean as described in a few other threads here).

Run a good fuel system cleaner through....such as Redline (available at advance auto parts) or Chevron Techron (available at many auto part stores)....If you have not done it for a while......give it 2 treated tanks of gasoline back to back. The bottle of Chevron Techron that I used...stated "treats up to 12 gallons".....I added 2 bottles to a tank of gasoline. The Redline....1 bottle will treat a tank.