4.3 TBI stumbles when warm
 

My son got his first truck and has some issues. It's a 1994 S10 4.3 TBI. 2wd, auto. 132k miles.


It runs like a champ for about 5 mins. Then it falls out its face has zero power almost. Barely can pull itself to 30-35mph without bucking and stumbling and surging.


I have replaced IAC, ICM, and fuel filter this weekend and still no change.


It know will run a rev up in park or neutral, but immediately dies when placed in gear.


Any thoughts?


Thank you!

Some possible causes come to mind:

- Coolant temp sensor. Does the dash provide temp indication that looks correct? The other sensor is for the overheat warning light if i'm correct.

- Battery voltage (do yo have to jump start the car?) Below 9 V on the electrical system the IAC is not working. Same if voltage goes over 16 V. Check with car gauge or volt meter

- Electrical and wiring problem with the sensors. Check all electrical connectors - clean, spray with a contact spray. Check wires for grounding and damaged insulation.

- TP sensor (at closed throttle the voltage should read below 0.85 V)

- TBI fuel leaks? (you would have smelled that one)

- Injector harness (damage or disconnect)

- Check that both injectors actually work. Spray pattern should be visible. CAUTION with open air filter element! FUEL = ignitable! Make sure you understand the precautions and safety measures to be taken.