Stalls in drive

HEAVYMETAL1458

MEMBER
1993 GMC C1500
5.7L
V8
2WD
AUTOMATIC
50 MILES

Start truck rough idle very low, eventually shuts off. Checked plugs were covered in black soot. Rebuilt engine five months ago, rebuilt transmission in December. New plugs, cap, rotor, wires, rebuild TBI kit, TPS, IAC, fuel filter, fuel pump, ect sensor, fuel pressure regulator, timed correctly at 0, get codes 15, but that is heating issue, gets fuel no problem, spray pattern seems good and wide. Just wont idle. Checked for leaks over and over, none. Checked wires all good, I know it is something minor but seems major. As soon as it starts less than 30 seconds it is dead. New distributor and module. I am really lost here, but wont quit I have invested too much money and time. It ran perfect two weeks ago then some bone head idea I got was to install a adjustable fuel pressure regulator but it wouldn't hold pressure. The gauge was leaking so I went back to stock but now it wont stay idle. Just before it just shuts off now. I did get to drive it and it had no power what so ever. Now it just starts and runs really rough or shuts off in 10 seconds.

2 Replies

ASEMASTER6371

MECHANIC
52,797 POSTS

Good morning,

What is the fuel pressure? It should be 9 to 13 lbs.

Did you replace the idle air control on the TBI?

Roy

NOTES:
If the IAC valve was removed during service, its operation may be tested electrically with the IAC/ISC Motor Tester (J-37027 or BT-8256K) or equivalent. Before installing a IAC valve, measure the distance between the tip of the valve pintle and the mounting surface. If the dimension is greater than 28.0 mm (1.10 inches), the valve pintle must be retracted to prevent damage to the valve. This may be done electrically using an IAC/ISC Motor Tester or manually by exerting firm pressure, as shown in the illustration, with a slight side to side movement on valve pintle to retract it.
No physical adjustment of the IAC valve assembly is required after installation. The IAC valve pintle is reset by turning the ignition ON for ten seconds and then OFF. The ECM then resets the pintle to the correct position. Proper idle regulation should result.

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