Even though the Check Engine light is not on, you still should check for stored diagnostic fault codes. The light is required to turn on only when the problem detected could have an adverse effect on tail pipe emissions. A failing crankshaft position sensor will not increase emissions because the engine won't run. Along those lines, the air gap of that sensor is critical. If the correct spacer wasn't used at some point, such as when the sensor and / or transmission was replaced, the signal could drop out momentarily. That will cause the Engine Computer to turn off the automatic shutdown (ASD) relay which turns off power to the ignition coil pack, injectors, alternator field, oxygen sensor heaters, and fuel pump or pump relay. It takes a couple of seconds for that relay to be turned off, so the engine can stumble or hesitate in the meantime. A few sporadic pulses will keep that relay turned on, and keep the engine running poorly, until the sensor's signal clears up. On the scanner's display, you need to watch the camshaft position sensor and crankshaft position sensor to see if they're listed as "no" or "present". The ASD relay should be listed as "high" when the engine is rotating, (cranking or running). If it goes low momentarily when the problem occurs, it is almost always associated with one of those sensors or their wiring. One clue you observed already pointing against a sensor is that the stall doesn't show up with the tach. The tach will normally drop to "0" when one of the signals from those sensors goes away.
If the cut-out or loss of power occurs for more than a few seconds, and if the ASD relay is still shown as "high", suspect a problem with either of the individual systems, the fuel pump / fuel supply, or the ignition coil. An ignition problem typically causes a sudden cutout and sudden restart, like you flipped a switch, while a fuel supply problem will cause a gradual loss of power over a couple of seconds. Unlike GM fuel pumps that typically quit while you're driving and let you sit on the side of the road, Chrysler pumps almost never do that. They often fail to start up when the brushes in the motor are worn, but once they're running, they will continue to do so until you stop the engine. That doesn't mean there can't be a wiring problem with the pump circuit. If I had to suggest the most likely places to find an intermittent problem with the pump, I'd look at the electrical connector at the tank and the fuel pump relay. If the fuel pump relay's contacts become pitted, the pump could slow down or quit randomly. As a test, switch the fuel pump relay with another one like it, then see if the problem still occurs.
I have a '95 Grand Caravan with the 3.3L that does the same thing you described, but only about once a month. It happens so seldom that I haven't pursued it but the best approach is to connect a scanner that can display live data and has a record function. I have the Chrysler DRB2 and DRB3, but there are similar aftermarket scanners. You press the "record" button when the problem occurs during a test drive, then you can review sensor data slowly, later, when you play back the recording. Since that data passes through the scanner's memory, the recording actually starts a few seconds before you pressed the button.
Monday, January 9th, 2012 AT 3:42 AM