Chevy stalling and surging

[94singlecab350]

I have a Chevy 350 that keeps surging and stalling it’s a 1994 with tbi i notice when it surges and I add a spray of starting fluid it starts to run normal.
Also I disconnect the negative Cable from the Battery and it dies.idk what the issue could be PLEASE HELP

 

[GoToGuy]

What were you supposed to find pulling the battery cable while it's running? Not recommended by the way.
How about a fuel pressure check first? Scan for codes?

 

[Schurkey]

Disconnecting the battery while the alternator is still charging is causing a voltage surge that can fry the alternator.

What is your charging voltage? Maybe the alternator has already popped.

As for the engine-running issue,

The Usual Three:

1. Verify fuel pressure at prime, at idle, and under load. Most fuel pressure gauge assemblies have a push-button pressure release connected to crappy vinyl tubing. Route the tubing so it empties into a drain pan, then push the button while the engine is running. This simulates higher fuel demand if you can't check fuel pressure on the highway. Fuel pressure should remain steady even with fuel flowing down the pressure-relief tubing. How old is the fuel filter? Have you ever dumped a bottle of Chevron Techron Complete Fuel System Cleaner into the gas tank? (Recommended at every oil change.)
   
2. How old are the usual “tune-up” parts and procedures? Inspect/replace distributor cap, rotor, plug wires, spark plugs. Make sure the ignition coil will reliably fire a spark-tester calibrated for HEI when the coil is fully warm, and misted with water from a squirt-bottle. Cranking compression test of all cylinders while the spark plugs are removed. Verify EGR, PCV, EVAP, and Heated Air Intake (if used) systems for proper operation. Verify proper initial timing (TBI) and electronic spark advance (TBI and Vortec). Replace old O2 sensors unless you can PROVE that they're working properly—old O2 sensors get lazy, they don't provide accurate data, but they do provide “data” that fools people into thinking they're “working”.
   
3. Connect a scan tool (NOT a crappy “code reader”) and look for “codes”. More important, look at the data stream to verify EVERY sensor and computer output. Verify fuel trims during the time that the vehicle is not running properly. Look for misfire counts for each cylinder (OBD2 only.) “Codes” have official diagnostic procedures that will be found in the service manual set for your vehicle. The service manual set can be downloaded from the links in the Sticky thread section of the Engine forum on this web site.

 

[Erik the Awful]

If you're trying to quick-and-dirty test the alternator, you remove the positive cable, not the negative. Everything should die when you remove the negative.

 

[Schurkey]

Removing either cable can cause alternator damage, and is NOT RECOMMENDED.

 

[Erik the Awful]

If your alternator is charging, your voltage shouldn't drop when disconnecting the positive cable, and you won't get a voltage spike. If your alternator isn't charging, you can get a significant voltage drop, which can cause a spike and could endanger other components. The alternator is not a worry because it's already dead or the charging wire is broken. You would be more concerned about the ECM.

Running strictly on the alternator without the battery will provide a more erratic voltage. The battery acts as a buffer for the electrical system, smoothing out the voltage ripples produced by the rectifier.

On the favorable side, pretty much everything has spike protection, but your safety is not guaranteed. Try and get the cable off in one movement. If you get spastic and drag the terminal across the lug, sparking it, you can get voltage spikes.

 

[Schurkey]

If your alternator is charging, your voltage shouldn't drop when disconnecting the positive cable, and you won't get a voltage spike.

GM disagrees...but I don't have a scan of that service bulletin. I'll see about getting one when I get the scanner set up.

 

[Erik the Awful]

Voltage spikes occur when a drop in voltage causes a magnetic field to collapse, inducing current in the wire. If the voltage in the wire and the battery are off by a volt or so, the field ripples, but doesn't collapse.

If the alternator is dead and you drag that terminal end across the terminal, then you're creating a bunch of collapsing magnetic fields, which ramps up your chances of creating a voltage spike. That is a danger to electronics that don't have shielding.

I called it "quick and dirty" for a reason. It works, but you're taking a small risk. The more electronic the car, the less I recommend it.