Hey Guy's I need a little help here.
I helped my brother convert his SB400 to TBI.
We got the throttle body from a 88 305, the computer,module,knock sensor,egr solenoid,MAT sensor,and Injecters from a 1990 Caprice350.
I set the Timing to 6deg before TDC and the truck runs good at Idle(most of the time)the only codes the computer throws is for the fuel pump relay and the VSS,and since he has a TH350 we are not using this feature.
What the problem is,is that the fuel pump relay was crap and we just directly wired the fuel pump to 12volt source out of the fuseblock.
While driving, the truck has a Tip in stumble,then it clears up till about 1.6 volts on the TPS,then it seems to stumble bad and bog down,then clears up a little and bogs down really bad at WOT.
The new fuel pump relay will be here today,and all the numbers on the scan tool look good.
What else could I be missing,Also when decelerating the truck will surge and stumble sometimes.
This thing is making My GrandNational look easy to tune.
Sorry so long I just wanted to be as descriptive as possible.
Thanks:Bildo:hail:

 

First off the 350 caprice eprom is probably screwing things up. It's a funny natured beast with it's odd VE tables. My advice is to use my ecu file over at diy-efi.org and get GM edit v2.0, use the same eprom burner you used when you were tuning your GN since it's the same eprom size/brand. It's that simple. I'd start off with some major calculations on fuel delivery. Seems like TBI has most of it's problems in this area. You'll also want to make certain that the timing tables are dead nutz on the mild side or you'll run into ghosts. You don't need a 350 ESC so don't worry about that so much. Just concentraite on getting enough fuel for max load and WOT and keep it clean at idle. Depending on the exhaust, head, cam, intake you'll most likely need a LOT of accel enrichment. You'll have to do this with the eprom or you can try and patch job it with a vacuum referenced FPR. What injectors are you using, what heads, cam, please go into more detail. Fuel pressure, base timing, that sort of stuff is always important.

 

Thanks J
While waiting for a reply on my post I went back up to my brothers and started over.
The new fuel pump relay is in and works great.
The engine is basically stock except for a set of long tube headers and a summit cam(204/214).I never personally had to burn a chip for my GN I have one that Jim Testa has done up for me.
Should I go and scout out a 1227747 from a wrecking yard,and start from there?
As far as the Fuel pressure I have no idea as of right now what it is, the fuel pressure gage will be here tomarrow.
Also why does everyone say you have to have the 350 esc and knock sensor when using the 350 injectors?
Thanks again for the help.
Let me know if your intrested in burning a chip for us.