Chrysler Repair: 97 Chrysler 3.8L van stalls in hot weather, gas gauge, hot weather

Question
Hi Roland!
I have a 1997 Chrysler T&C LX minivan 2WD with a 3.8L engine that has recently begun stalling intermittently in hot weather, normally above 85 degrees F, at least 20 minutes into a drive.  The stalling occurs when the car is turning to the right only, though sometimes (and this is usually when the outside weather is well above 90 degrees) it will later occur on straightaways after it has been stalling a bit when turning (or curving) right.  When this happens, the car usually just stumbles at first for 15-30 seconds and doesn't completely quit, but later in a drive(when the car's engine is hotter, i think) it may completely shut down and will not start back up right away.  On really hot days when this has repeatedly happened on a long drive, my wife has had to let it cool for several minutes before it would start up and run again, and then typically happen again.  It never stalls on cool days.  The check engine light has come on several times when this happens, but it reveals no codes when I use my scanner.

I have recently replaced the alternator and water pump when these started having problems, and I just replaced the EGR valve as I thought it might be the cause, but now I realize from some of your postings that that's more of a stalling when idling/low RPM problem when cold issue.  Of note, for several months before this started happening, the gas gauge has been going haywire, from time to time showing no fuel and setting off the low fuel warning light again and again despite the tank being close to full.  As I'm thinking that is might be a fuel delivery issue, I thought that might be relevant.  
Thanks for any light you can shed on this baffling problem,
Paul  

Answer
Hi Paul,
Hesitation/stumble with no codes appears to requires looking into almost all the engine control systems (some 17 of them) according to the van powertrain manual I have for '96.
But before doing that we can think about what might explain this being associated with a fully warmed up engine. The system that comes to my mind first is the coolant temp sensor which is located next to the thermostat housing (and under the spark coil according to the drawing in that manual). Using the Chrysler DRB reader allows one to compare the temperature at the housing with the reading based on the sensor, rather than the resistance of the sensor as a function of its temperature. If your reader doesn't give a temp reading then use an ohmmeter to see if the resistance varies smoothly from cold to very hot. It should start in the range of 7-13k ohms cold and drop to 700-1000 ohms at 200F and continue down smoothly to the highest temp you can get to at idle. There may be a discontinuity in your present sensor that appears at high temps.
Another temp sensitive element is the Hall effect type sensor used for the cam and crank position signals. Normally when these fail they would set a fault code, but I can imagine that in the early stages of failure that the signal might be intermittant or degraded but no so much as to cause a code. You could measure the variation in the voltage pulses between the sensor signal and ground wires while turning the engine over by hand using a breaker bar and socket on the crank pulley bolt. The signal should vary between 0.3 and 5.0 volts if it is o.k. in synchrony with rotation of the crank. You would have to probe the sensor wires with pins to make connections. The ground wires are black/light blue and the signal are gray/black and tan/yellow, respectively. The orange power supply wire should have 8 volts on it.
Because of the relationship to turning (though you said it ultimately will stumble when going straight) it might be good to try manipulating all the harness wires once the engine is hot to see whether you can find one with a flake connection such that the engine will stumble when you shake it.
Those are the items I would check specifically at the time the engine has stalled out. Another mixture controlling sensor is the MAP and that similarly could be monitorer for voltage discontinuity as it is heated up and the engine is idling, and also shaking its harness.
Other than going thru all the checks of those other systems, you may just have to wait until a code appears.
Please let me know if you find the answer.
Roland