Van lost mileage

Seems to me if you switched plug wires you'd have a bad miss. Any chance the distributor is loose and you accidentally turned it while changing the cap? Or perhaps the vac advance hose got knocked off?

Life isn't being fair, now. Last friday the van didn't want to start, took an hour and a half, and a battery charger. A couple months ago, the EGR valve went bad, stuck shut. I plugged the vacuum line. So, it may be a vacuum line came loose, never know. Or the bad EGR is causing all kinds of problems. In the meantime, it's bitter cold out, and I've got nine inches of snow out there. I'm going out later after a hearty breakfast, and clear some snow. I'm driving the Blazer, for everything, for the meantime. Had to happen in the winter, of course.

Dad's snow blower won't start, when we need it the most. I suspect water in the gas. It's 20F, unheated garage, and I'll be working with metal tools, and cold liquids. Not fun. But, such is life.

A quick shot of ether will tell you if it's a fuel problem, and often gets it started AND drawing fuel through a slightly restricted jet.

Just a breath of ether though, or you CAN do damage.