Sorry it took me so long to get back. I'm getting lunches ready for tomorrow.
I know the 2.8/3.1 engine very well.
Take the intake hose off of the throttle body.
You should be able to stall the engine if you put your thumb over the hole in the bottom of it right in front of the flapper, (the port that the idle control is connected to)
if it doesn't stall then you have a vacuum leak in the plenum or the intake manifold
Wednesday, November 8th, 2017 AT 1:49 PM