Engine randomly shuts off, sometimes I can drive for 5 minutes sometimes an hour?

That relearning applies to sensors because no two are ever exactly alike. The process usually takes just a few seconds, and you'll rarely notice any performance issues.

As for the fuel pump, those take a lot of current so they're always turned on and off through a relay. The low-current coil side of the relay is the only part the computer sees, and that is the same for any replacement relay. As for the contact side, the computer has no idea of how much current is flowing or whether it's excessive or too low. It doesn't even know what is being powered up.

The only other variables related to the fuel pump are pressure and volume, but even those are irrelevant. The pumps can develop as much as 70 psi if the fuel line is blocked. During normal operation that fuel passes through a spring-loaded pressure regulator valve on the fuel rail on the engine. That holds pressure down to around 45 to 50 psi, and that changes a little from changes in manifold vacuum. That's why there's a vacuum hose plugged into the regulator. When you're coasting, vacuum goes way up, and that being one of the two forces acting on a molecule of gas, would pull the gas from the tip of the injector into the engine too aggressively leading to a very rich coasting condition. By tying it to manifold vacuum, that tugs on the spring-loaded valve so it opens easier, thereby lowering fuel pressure. Higher pulling force coupled with reduced pushing force equals a steady fuel flow that prevents that rich coasting condition. As long as the pumps can maintain a pressure higher than the regulator is set at, every replacement pump will develop the same pressure in the line, so there's nothing to learn there.

The other issue is pump volume. This is another big area of confusion and is directly related to that stalling due to the plugged screen I described. Every pump is going to move a good one or two gallons per minute. That is what has to get through the strainer. Way less than one percent of that gets diverted to go through the injectors into the engine. Well over 99 percent goes through the pressure regulator, then back into the tank through the smaller-diameter return line. The strainer can be plugged enough to drop fuel volume to the point that only enough gets through to meet the needs of the engine. That leaves nothing to go back through the regulator and return line. If the blockage gets just a little worse, fuel volume becomes less than what the engine needs, then you have hesitations, stumbling, or stalling.

To finish my story on the strainer, when you're coasting and manifold vacuum goes up real high, the fuel pressure regulator drops pressure so the total of the two forces acting on the fuel remains steady. Dropping pressure means the fuel finds it easier to flow through the regulator, and that is what makes volume go real high. When the strainer is plugged, the volume isn't high enough. That results in the symptom of stalling due to fuel starvation when coasting, and the engine runs better when accelerating or cruising, which is when it burns more fuel. The confusion comes from the volume of fuel being pumped, or circulated, and the volume of fuel going into the engine are opposite. One goes up when the other goes down.

So now let me answer your question a better way. The computer doesn't learn anything related to the fuel pump. As long as there's plenty of fuel volume, and the correct fuel pressure, the only things that affect that are the fuel pressure regulator and the strainer.

Chrysler is the only manufacturer back then that never used a mass air flow sensor or needed them to make their engines run right. That was something else you cleaned.

I know you're listing everything you've done, even those things not related to this problem. Keep in mind things like spark plugs don't all stop working at the same time, so a lot of similar parts will not be good suspects. Also, while this has nothing to do with stalling, the goal of the intake system is to warm the air so gas will vaporize easier. Liquid gas doesn't burn. It has to be in vapor form. Cold air intakes make that less effective.

In looking back, unless I missed it, I didn't describe how most scanners have a "record" feature. That, along with the fuel pressure gauge, is what we need to solve this. You drive around with the scanner connected, then, when the stalling occurs, you press the "record" switch on the scanner. Because the data travels through the scanner's memory, the recording actually begins a couple of seconds before you pressed the switch. Later that few seconds of data can be played back slowly to see what changed. For the stalling, we'd watch the crankshaft position sensor and the camshaft position sensor to see if either signal dropped out. Both are needed for the Engine Computer to keep the automatic shutdown, (ASD) relay turned on. That relay sends current to the ignition coil(s), injectors, and fuel pump or pump relay.

If one of those sensors is responsible, you'll also see the "ASD Request" switch to "off", and the listed engine speed will drop instantly to "0". If this is a fuel-related problem, engine speed will gradually drop down until stalling occurs. While coasting to a stop, the transmission will keep the engine rotating down to around 20 - 30 mph, and since this isn't a sensor problem, engine speed will continue to show up as it slows down gradually. Of course if this is fuel-related, that would also show up on the fuel pressure gauge.

There was a common problem with the ignition switches in some models, but that never caused stalling. There's three or four parts to that switch. One of them developed overheated contacts or an overheated pair of connector terminals, and either one would lead to the other. That was for the high-current accessory circuit to include the power windows, radio, and heater fan motor. The problem occurred most often to owners who usually switch the ignition switch on and off while the heater fan is set to one of the higher speeds. That results in heavy arcing on those contacts, and that leads to them overheating.

The ignition switch and lock cylinder are replaced separately, so a failure of one doesn't mean the other one had to be replaced.

My guess is the "1-5" he was referring to had to do with the throttle position sensor or the MAP sensor. Those are fed with 5.0 volts and 0 volts, (ground), then they develop a signal voltage between 0.5 and 4.5 volts. Those are the voltages we use for training and explanation purposes. In real life, you might find 0.42 and 4.71 volts. The point is they can't reach 0 or 5.0 volts. The TPS has mechanical stops to limit its range to 0.5 to 4.5 volts, and the MAP sensor has circuitry that will do the same thing.

It's when there is a defect inside the sensor or with its wiring that a signal voltage can make it to 0.0 or 5.0 volts, and the computer sees that and sets a diagnostic fault code in response. In fact, it's those voltages that are what the computer looks at when testing the circuits. Temperature sensor circuits work a little differently, but the same range of voltages apply.

Remember, if your mechanic did any type of testing with electronic equipment, that didn't include fuel pressure and volume, so he wouldn't have seen a problem there. Please keep me updated of any developments.

There's too much confusion to know where to go next. Your mechanic gave you some numbers, but we don't know what they refer to, so we don't even know if those have anything to do with something that could cause stalling. I haven't seen any fuel pressure test results, so we don't know if we have to look at the fuel supply system or move on to other systems. You have a new fuel pump with strainer, but there's also wiring that can have a corroded splice or connector terminal that causes intermittent operation. We would only see that on the fuel pressure gauge as fuel pressure isn't monitored by the Engine Computer.

Just about every repair shop has a scanner with a "record" feature that will record a few seconds of data that can be read back slowly, later, to see what changed when the problem occurred. That hasn't been done either. You can see why this is like asking your doctor for a diagnosis, but he hasn't run any tests yet. Engine Computers do fail from time to time, but in general, that's the first thing people think of, but usually the least likely item to solve a running problem. If you want to substitute the computer, there's nothing to program for a '96 model. I'd head to a pick-your-own-parts salvage yard to find an inexpensive replacement to try. Do a search for "Pull-A-Part" to see if they have a yard near you. They have about two dozen yards, mostly between Ohio and Georgia, but now also a few to the southwest. Their yards are extremely clean and well organized, employees and customers have always been very friendly and helpful, and parts are inexpensive. There's more and more yards like these popping up all over, but none are as clean and well-organized.

I should point out too that if you replace the Engine Computer, which obviously means unplugging it, or if you disconnect the battery, the computer will lose its memory. Most of the learned data will be rebuilt as soon as you start driving, without you even noticing, except for "minimum throttle". Until that is learned, you may have to hold the accelerator pedal down 1/4" for the engine to start and stay running. You won't get the normal idle flare-up to 1500 rpm for a few seconds after start-up, and it will tend to stall at stop signs. To meet the conditions for that relearn to take place, go out and drive it at highway speed, (with two feet if necessary), then with the engine warmed up, coast for at least seven seconds without touching the pedals. The computer will again be in control of idle speed at the end of that seven seconds.

Hi,

I noticed it's been a few days. Have you made any progress with the issue? We are very interested in knowing.

Thanks and God Bless,

Joe

Hi,

I looked at your pics. The short-term fuel trims are indicating fuel being added. Have you checked for vacuum leaks or the fuel pressure? Also, the coolant temperature sensor says 95°F. Was this done as soon as the vehicle was started and still not at operating temperature?

Let me know.
Joe

Hi,

If it was running for five minutes, the ECT should have been higher. I'm starting to question if that is the issue.

Do me a favor. Allow the engine to reach operating temperature. See what the ECT signal is at that point. It should be around 200°f.

Also, here is a link that explains how to check for a vacuum leak:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Let me know what you find.

Joe