Please Help I’m lost!

[Wastedwages]

I have a 2002 crownline with a 2001 5.0 merc efi. I seem to be chasing a ghost! Sometimes it will start right up and hiss at me other times it starts hard and I have to pump the throttle to get it to start then I purrs like a kitten. Merc dealer had it a month replaced IAC, fuel pump, fuel pressure regulator. We were making no head toon so I brought it home. So far I have replaced cap, rotor, ignition sensor, air!temp sensor, coolant sensor, map sensor ,battery, plugs and wires. When it runs it runs good but an sob to start. Codes that were in ecm 22,23,25, and 34. Swapped out iac tonight with old one and it seemed to run better and start better but still had to pump the throttle.water temp runs 175 oil pressure is 50-60psi. What am I missing?

 

[QBhoy]

Obvious one would be to ditch every drop of fuel out that fuel tank. New filter and see how she goes.

 

[Wastedwages]

Filter is new I forgot about that. Tomorrow afternoon I may empty out the rest of the 91 in the tank

 

[Bt Doctur]

pumping the throttle on a EFI or MPI does nothing

 

[Wastedwages]

Read on a post that if it starts that way it needs iac replaced. Say what you want, I would agree with you normally but you can crank on that starter til the battery runs dead but if you pump the throttle it starts. I see the dealer did not replace the base gaskets and the 90’s tbi trucks went thru them left and right so I am going to do that tomorrow also