Starts and runs OK from a cold start, down the

to get to the back 3 plugs its easiest to have the van on the lift and go up from underneath beside the exhaust. thats about the only way to get to them

I had a chevy truck that used to do the same thing.. I replaced the fule pump, distributor , and put a lot of $$$ in it before a localechanic found the problem... It was a flaky control module (main brains of the sustem).. Replaced it and no moe probs..

re: your spark plug issue.. I worked n a repair shop whilein high school. The master mechanic there used a hole saw just big enough for the plug socket to et through and driled a hole in the inner fender.. You pull the tire off and with a socket extension the back plugs are easy access.. one time fix takes care of all future plug changes.