Falls flat under acceleration

[BILL NIVEN]

1990 Silverado K1500 5.7 automatic. Under normal acceleration the truck runs good. Pull out to pass accelerating from 50 mph it has no power and spark knocks pretty bad. You can feel passing gear kick it but will not accelerate.
I have a new TBI, IAC, fuel pump and filter, plugs, wires, ICM, cap and rotor, converter and rebuilt trans. I have replaced every sensor under the hood but no change. Verified initial timing at 0 degrees with computer disabled. Fuel pressure checks normal at idle, had to add Schrader valve.
I have a new distributor but not installed yet.
I am a shade tree wrench Turner and its obvious I have missed something. Any suggestions would be appreciated. I prefer to do my own work and not take to shop.

 

[mistaake]

Install your new distributor Have you checked fuel pressure under load?

 

[BILL NIVEN]

Install your new distributor Have you checked fuel pressure under load?

Can you tell me what the fuel pressure under load should br?

 

[Phillip Buessing]

9-13psi, preferably on the higher end

 

[whiteboyslo]

How does one check while under load, though?

Mike

 

[PlayingWithTBI]

You have a schrader valve, just get a 1/4" fuel line hose and rig it up with a quick connect to your pressure gauge. Pressure should be at least 11 psi. You can download TunerPro RT and buy an ALDL cable to data log, if you want to know what's really going on..

http://www.tunerpro.net/
http://aldlcable.com/aldl.asp

Did you calibreate your TBI after you changed all of those sensors?

http://www.gmcmidwestclassics.org/Web pages/Tuning the TBI.pdf

 

[PlayingWithTBI]

Here's the 2nd thread

1990 Silverado K1500 5.7 automatic. Under normal acceleration the truck runs good. Pull out to pass accelerating from 50 mph it has no power and spark knocks pretty bad. You can feel passing gear kick it but will not accelerate.
I have a new TBI, IAC, fuel pump and filter, plugs, wires, ICM, cap and rotor, converter and rebuilt trans. I have replaced every sensor under the hood but no change. Verified initial timing at 0 degrees with computer disabled. Fuel pressure checks normal at idle, had to add Schrader valve.
I have a new distributor but not installed yet.
I am a shade tree wrench Turner and its obvious I have missed something. Any suggestions would be appreciated. I prefer to do my own work and not take to shop.

 

[BILL NIVEN]

Reset the TBI? I cleared and reset the computer with jumper wire between A&B terminals.

 

[PlayingWithTBI]

Reset the TBI? I cleared and reset the computer with jumper wire between A&B terminals.

I'm not sure what you mean about reset the TBI? By jumping terminals A & B you're getting stored codes in the ECM. It will still retain those codes until a certain amount of key restarts or, you can disconnect the negative terminal on the battery and short that cable to the positive terminal to drain all capacitors in the ECM. What I was talking about in my previous post was calibrating the TBI. When you install new sensors, you need to calibrate them for your TB and throttle cable. HTH

 

[BILL NIVEN]

Install your new distributor Have you checked fuel pressure under load?

Fuel pressure under load was 12psi.