96 454 MPI missing under load when warm
 

Any suggestions/ideas are appreciated. I have a 96 454 MPI SKI engine. It starts off occasionally missing at 3/4 and above throttle and gets signifcantly worse as the engine warms up to the point it won't do anything other than idle. It takes a good 15 minutes after it has warmed up to really start acting up. It starts everytime and idles perfect.

I have take apart the VST assembly and cleaned the filter. The fuel pressure is about 32 psig at idle and about 35 psig as the throttle opens. There is no drop in fuel pressure when the engine misses. The cap/rotor/wires/plugs are all new this season. Any ideas out there. Thanks,

ERIC

mrfixxall
 

Bad pick up coil in the distributor,coul,coil wire or loose filter and or fuel lines.

Thanks, the distributor probably needs replacing as there is some corrosion on the inside of it.

The plot thickens however, I started it again and let it idle for about two minutes. The temp. gauge hadn't even moved yet and I tried bringing it on plane and it backfired and stalled. From then on, it would only idle for a few seconds then die. I let it sit for 5 minutes and it then ran fine until it warmed up and started doing what I said above.

What is the best way to get the codes out of this thing. I can borrow an OBD II scanner. Is it different than what the marina has to trouble shoot?

mrfixxall
 

i had a 454 385 hp mpi thaat did the same thing as you are discribing..one of my customers had a impeller put in his boat and the guy that worked on his boat had left the fuel line going to the filter housing finger tight..it wouldnt leak fuel but it sucked air and not fuel through the filter housing..

you need a merc scanner to read the codes..