Why would a stock 1990 5.0 not start when its cold, then as it warms up during the day it fires up and runs perfect til night and then will not run until warmth the following day. Did not do this until engine shampoo a few days ago. Plenty of time for everthing to dry out. I don't get it ???
I remember having a similar problem. I hosed down a hot enginge years ago and cracked something. temperature had everything to do with how it worked from then on. Not sure but I think it was a tps. replaced the part and went back to normal.