Ok got my new 383 engine in and have been driving it. The car idles fine but doesnt have good throttle reponse which was the same with my 305 that was in it. Also I have a AFPR and with the 305 it was at 40psi I think and I set it to 50. I ran well but off stop lights at normal accelaration it would miss at about 1500. Well dropped the new engine in and after timing and valve adjusting any everything it was running pretty good. I didnt touch the fuel pressure. It ran a little ruff with the cam and pulled hard all the way to 5 grand. Then my Fuel Pressure Regulator started pissing fuel out of the vacuum line. I replaced the regulator and backed the adjustment screw all the way out. The car ran a little better at idle but it gave me the 02 sensor lean code. I hooked a fuel pressure gauge up and it was sitting at 50 psi! With the regulator set at what I had it on the 305 it must have been so high it blew it up. I thought well I might as well give it a little more since its running lean and bumped it up to 55. Ever since the regulator blew up and I unscrewed the adjuster the car still has bad throttle response and when you nail it its bogs a little and doesnt pull hardly from 3 up anymore. Does this sound like a bad Fuel pump? Thats the only thing I can think of. I have 30lb injectors so I dont know why I would have so much fuel pressure without having the adjustment in at all but still bog when you get on it. I am really frustrated since I just spent all this time with the new engine but cant figure out a small problem. Thanks for you guys help in advance. Any questions just ask.

 

Did you get a custom PROM made for the new engine?

Sounds more like a computer problem than a fuel pressure problem. 30 lbs/hr. injectors at 55 psi should be enough to feed 500+ horsepower.

Keep in mind that fuel pressure has nothing to do with part throttle response, only WOT. At part throttle the computer reads off the O2 and adjusts the mixture accordingly.

 

Yea I got a custom PROM for this engine. It bogs whener you rev it and not just WOT. But if your driving it and you floor it it bogs a little then seems like its struggling but not making much power all the way up to 5 grand. Thanks for resonding.:yourock:

 

What's your TPS voltage set at?

 

Dont know, on the 305 I had it set at .5 and it didnt have good throttle response.

 

.57 is the factory setting. Going up to .62-.65 is an acceptable way to cure a stumble like this. Try the factory setting first and see if it gets better. If not adjust to the range I mentioned.

Sounds like you are experiencing a lean bog. The TPS adjustment should help, if not eliminate the problem.

 

Ok that will help the throttle response maybe but what about how the car isnt making power above 3 grand? Thats what really is making me mad because it isnt making hardly any power but it pulled hard before when my fuel pressure was really high.

 

How did you have your custom PROM made? It sounds like something is way off with the programming.

 

Also, have you checked what your running fuel pressure is? The fuel pumps ability to deliver enough volume and pressure isn't constant. Readings taken at idle, or when the engine isn't running don't tell you the whole story. You need to see what is happening with the pressure at different RPMS and loads.

 

I'm going to barrow a scanner or a volt meter and adjust the TPS and check the fuel pressure when you rev it and such to see if it dips at all tomarrow. Thanks.

 

You really need to check it while driving the car too, because if you just rev it the engine isn't under load.

 

I didnt get around to checking the fuel pressure but I have a question. I was thinking I would unplug the MAF to make it run rich. I unplugged it and from the past I was expecting for the check engine light to come on. Well it didnt. The car ran a little ruff but that was about it. I drove it a couple blocks then shut the car off and plugged the MAF back in and started it and it ran like it always does. I later checked my codes and I didnt have any. I thought that if you unlug it should take a second or to then the light comes on... Whats up with that?

 

That's odd. I would think that it definately would throw a code. Did the car get up to operating temperature? The reason I ask is that, though I'm not entirely sure about this, the computer might not start looking for MAF values until the car is fully warmed up. It does this with the O2 sensor.

 

Fixed it, Timing problem. Let me describe it as this, going down the highway next to a Stage2 Roush threw it in 3rd and held it sideways at 80+. Hit Fourth hooked and smoked the Roush really bad. I love how much power this thing has.