I was referred to this board by a guy on another 4x4 website. Apparently, this is the site for TBI.

I am building a 89 Suburban as a 4x4 off road truck, and I am using the stock TBI. I have had the motor re-built with flat top pistons, decked heads, and a rv2 cam.

Here is the problem, the truck will not run, it seems like it is starving for fuel. If I take the vacuum line off of the MAPP sensor, the truck will idle fine, but you cannot put any throttle on it or it falls on its face. I put new injectors in it, a new throttle posistioning switch, fuel filter, I rebuilt the TBI 3 different times, and I tried a new MAPP sensor but that didn't work either. This is very frustrating as I am 2 years into this project and this is the last thing I have to do. Any help would be great as I am about to say screw it and go back to a carb for a bit.

 

Start with determining the fuel pressure.