454 mag mpi running rich!!!
 

I have pulled the plugs and they are completely black. Standing behind the boat it smells rich. Its using a gallon of gas at idle in 20 minutes or less. Timing is at 8 degrees...I assume that's correct. I'm using Autolite 25 plugs.... should I use a different plug and timing? I guess wires, cap and button are in order? What else can cause these https://cimg8.ibsrv.net/gimg/www.off...48e993abad.jpgefi engines to use so much fuel or are they just that thirsty?

You need to put a scanner on it. Coolant temp sender, thermostat stuck open, map sensor bad, lots of things that can cause it.

Adding more to the list of what can cause this --- weak ignition output and or overflowing fuel injectors and or Dirty flame arrestor next possible -- .Bad t stat - or wrong lowered temp t stat installed ?.

The tiny STOCK flame arrestor on the 97 and up big blocks very easily became restricted. This alone can cause rich conditions. Seen it many times.

If its ALL the cylinders id check coolant temp sensor first, if circuit is "open" the lookup table is -40, that adds 50% fuel, feiwhttps://cimg8.ibsrv.net/gimg/www.off...36f790c4fd.jpg

Your iboats thread list pressure at 30 psi

Wow 50% fuel for a coolant temp sensor!!!!!

I really need to check it closer. Im pretty sure its over 30 PSI but Im not sure how much over. The book states 34 to 38 I believe. Ill check the fuel pressure closer but considering its running rich and using alot of fuel I think I might just replace this coolant sensor....where is it?

Articfriends....it says cold choke....does this change after its warm?

Thats the thing, the sensor tells ecu how warm the motor is, if circuit is open (broken wire, unplugged sensor, open circuit in sensor) it will always think its -40 and go to max fuel multiplier. Id have someone scan it. When i tune a mefi boat i change all those numbers the boat will never see to no multiplier so someone dont wash their rings and destroy motor over a bad sensor

Wow that's really out there. Being told my motor may be a two wire and ECU may not adjust based on temp?

A scan tool will verify if the coolant temp sensor is working correct plus one can check to see if the temp gauge on the dash is reading the same temps as well.

Steve --- Is that the stock tune ? and what Mefi is the display from ? 60 thru 120 is reading Base pulse width modifier at 1 - that does not seem like the stock cal if I recall correctly ?