7.4 MPI very sluggish
 

i have a 1998 7.4 MPI that is a turd out of the hole takes forever to get on plane had a computer hooked up to it tonight and at wide open throttle the timing advance is only 15 degrees total if i ease into the throttle the advance will go up to 26 degrees total but after a certain point it drops to 15 the engine only has 200 hours on it i have changed computers, throttle bodys with the iac and tps, and distributors and nothing seems to make a difference base timing is set at 8 degrees BTDC it does not miss and there are no codes i lost about 10 mph from the old engine ( which i blew up ) to this one and i am pretty sure i will get that back once i get it running right anyone have any ideas ?? thanks Ed

Fixx
 

check the knock sensor for a good ground,if it senses any detonation ot mechanical lower end noise it will retard the timing..premium fuel helps too.. you can try unpluging it to see if it keeps the timing stable..

according to the computer the knock sensor is working but not sensing any detonation so it doesnt appear to be retarding the timing we took a hammer and was tapping the block by it and could see it working i have also tried premiun fuel and it didnt make a difference on another board someone said maybe it is a fuel delivery issue i never checked the fuel pressure but i will this weekend on the water

i found this module that is bolted to the back of the engine called a spark advance module but it is not going to be easy to get to to change it kind of wondering what some one elses thought is on this if it could possibly be the problem

Fixx
 

have you had your injectors cleaned? their are screens in the top of them and after they get plugged with cotton from the filter and causes the motor to go lein..send thsm out and have them back flushed and new screens put in them..you will loose about 1000 rpms if their plugged up..

ed
 

im having the some thing going on with my boat i have the same motor how fast is your boat and how long is it ? my boat started missing realy bad this weekend i wonder if i am having the same prob/. ?

my boat is a 272 baja and since i have changed engines this summer due to a major brain fart on my end the best i have gotten out of it is 48 going with the current on the saint clair river everytime i change something on it it has been getting slower to the point i couldnt get it over 9.5 mph last weekend only thing is mine doesnt miss a beat it will hit the rev limiter out of gear but wont get out of its own way under a load

i changed the injectors with the ones out of my old engine last week ran great friday night came on plane easier than it has all summer with this engine put it back on the trailer saturday afternoon put it back in the water with 2 more people and a cooler and couldnt get it over 9.5 mph there is no way maybe 400 lbs of extra weight slowed it down that much timing still would not get full advance and the fuell pressure was about 28 psi at wot and 20 psi at idle i am starting to think i might have a bad fuel pump but that still doesnt explain the timing not advancing

but that is why i bought my boat for the fuel injection i hate carbs i have had way more problems with them in my lifetime than i ever have had with injection until now