99 blazer "hiccups"

There is a recurring issue where after a period of heavy rains, my car has a hiccupping/stuttery start when pulling out/coming off stop light or sign. It resolves after reaching upwards of 35mph.

My car has about 85,000miles on it and recently did excellent on a cross-country trip from Washington DC to Seattle.

A week or two ago, it was doing the hiccup thing and figured it would pass like it normally does only to find it wouldn’t start. Had it towed to a shop which said it was out of gas and started when fueled, despite the fact it registered as 3/4 full and had only driven about 80 miles since fueling (normally gets about 200mpg city). They found the diagnosis also indicated MAP sensor needed replacing.

I had them change the MAP sensor and fuel filter, but not the gas gauge they said was probably bad due to the added labor etc for pulling the tank.

When I left the shop, I immediately went to fuel, but the pump shut off only after a gallon. I forced it to put in a couple more but it kept shutting off indicating it was full.

The next day I drove it, it was still doing the hiccuping and the engine light came on, only to go off the next day driving back to the shop. Mechanic said not to come in since if the light is off, diagnosis machine wouldn’t report what was wrong.

After all that, my ideas are that it could be 1)clogged fuel injector 2) sensor is acting up 3) exposed wire that is sensitive to moisture. Any idea what this could be??

I would take a look at the vapor recovery system.
Oh, and there is a memory chip that records codes even when the ck eng lte is out.