Question edited for clarity.
Question moved to model category.
3: 1988-95 5.0L, 5.7L and 7.4L Engines Firing Order: 1-8-4-3-6-5-7-2 Distributor Rotation: Clockwise.
Sounds like the starter solenoid or the starter itself - probably needs replacing but check the wiring at the starter first (loose connection, frayed wires, etc.).
Sounds like the pitman arm. See #5 on diagram below. It has a ball joint with grease that is held in with a boot. It the boot is cracked open, you should replace the arm. You will need an alignment after replacing the arm. The arm does not contain any steering fluid, so if that is leaking, you have another seal broken somewhere...
Retarding the timing will cool the combustion which will lower the Hydrocarbon number,it will run bad but after a passed e test put the timing back to an advanced state which may help with the stumble.
First check for a vacuum leak. Any small loose hoses in the engine compartment? If not, suspect the idle air control valve. I have pasted test procedures for the iac below. Be careful not to confuse the tps with the iac. The tps is centered on the ybro5ttle body. The iac is more on the perimeter. An additional test I do after checking the valve is to plug it back in while it is still off the throttle body and verify that it actuates a little when the key is turned on. It should back up a tad to allow idle air through the passage for starting.TESTINGDisengage the IAC electrical connector.Using an ohmmeter, measure the resistance between IAC terminals A and B. Next measure the resistance between terminals C and D.Verify that the resistance between both sets of IAC terminals is 20-80 ohms. If the resistance is not as specified, the IAC may be faulty.Measure the resistance between IAC terminals B and C. Next measure the resistance between terminals A and D.Verify that the resistance between both sets of IAC terminals is infinite. If the resistance is not infinite, the IAC may be faulty.Also, with a small mirror, inspect IAC air inlet passage and pintle for debris. Clean as necessary, as this can cause IAC malfunction.Fig. Fig. 2: Using an ohmmeter, backprobe terminals of the TPS sensor to check for proper resistancesFig. Fig. 3: The TP sensor and IAC sensor are usually located at the side of the throttle bodyFig. Fig. 4: Idle Air Control (IAC) valve wiring and terminal identificationREMOVAL & INSTALLATIONDisconnect the negative battery cable.Disengage the electrical connection.Remove the IAC valve. On thread-mounted units, use 1 1 / 4 in. (32mm) wrench and on flange-mounted units, remove the screw assemblies.Remove the IAC valve gasket or O-ring and discard it.To install:Clean the old gasket material from the surface of the throttle body assembly on the thread mounted valve. On the flange-mounted valve clean the surface to ensure proper O-ring sealingInstall the valve with a new gasket or O-ring. Tighten the thread mounted assembly 13 ft. lbs. (18 Nm) and tighten the flange mounted attaching screws to 28 inch. lbs. (3 Nm).Engage the electrical connector to the IAC valve.Connect the negative battery cable.
Most likely the switch has died. They over heat and melt inside and at the plug. Also look at the ignition wires under the dash, Sometimes they can chaff against the column or frame.
There are propriety brand sprays you can get at your parts store that will soften old gaskets. Be careful digging at the surface so as not to score or damage the surface.
Check your exhaust, see how much pressure you can feel coming out of your tailpipe. Sounds like a blocked catalytic convertor . Other issue would be the throttle position sensor. If you have check engine light in pull the codes I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_677dced97ad9bddf
It will be in the main fuze box under the hood or in front of your knees, because there are usually other things taken off that fuze. Check the fuze box lid and see if it shows the cig lighter but it may only show something like the blower of some other ancillary item. Go through the switches etc and see if anything else has failed, it might help. The alternative is that the fuze is good but your cig unit has failed. Don't rip the dash out until you are sure.
I would go get a new distributor because gmc and chevy trucks are known for the gear that runs on the cam to get a little worn out and then the computer doesn't know where to advance or retard the timing to. So try that. I had a similar issue and I tried everything under the hood and it was just what I discribed.
