1990 5.7 drivability issue

[Munch]

1990 c 1500 with 5.7. When I bought the truck, it had a stumble at 1st hit of the throttle. Didn't worry about because the truck was torn down for paint and body and new motor. Now I have it all back together and running and the stumble is still there. New fuel filter, tps is set. No check engine light. Once it stumbles it will clean up and I can rev it if the rpms are up. Let it come back to idle, blip the throttle and stumble. if I hit the throttle hard, it will stall. Where do I look next?

 

[RichLo]

Start with a routine tune-up and go from there

Cap/Rotor, plugs/wires, o2 sensors. If that doesn't fix it then go onto getting a TBI rebuild kit and tear that apart and clean everything inside. Those simple items usually fix 90% of run-ability problems with these trucks if a PO under-maintained it.

 

[Schurkey]

Scan tool--look at the data stream.

How old are the cap, rotor, plug wires, plugs?

Will the ignition coil fire an HEI spark tester?

What is the fuel pressure?

What is the cranking compression of all eight?

 

[sixteenacrewood]

I would pull the egr and clean it. Also general tune up stuff Richlo said

Get the Hains manual and a good digital multi meter and test all the sensors, there aren't that many and takes less than a half hour.
I try not to throw parts at problems anymore.
My bet is egr.

 

[Munch]

Start with a routine tune-up and go from there

Cap/Rotor, plugs/wires, o2 sensors. If that doesn't fix it then go onto getting a TBI rebuild kit and tear that apart and clean everything inside. Those simple items usually fix 90% of run-ability problems with these trucks if a PO under-maintained it.

I forgot to mention, new 02, new plugs, new wires, new cap and rotor. Where can I find a TBI rebuild kit? Something autozone will carry? Thank you for the info.

 

[PlayingWithTBI]

Where can I find a TBI rebuild kit?

Here's an option, you can do it yourself our they'll do it for you.

https://www.ebay.com/str/sprperformance

It sounds to me like your fuel and/or timing is off.

 

[xx94Z71xx]

my old 93 c1500 ran like this when the fuel pressure was low. was worse when cold. id check the fuel pressure.