Chrysler Repair: 3.8L 97 T&C continuing stalling problems when warm, air fuel mixture, camshaft sensor

Question
Hi Roland!

Thanks for your guidance written on 7/21/06 with this continuing problem with my 97 Chrysler T&C 3.8L van with 121K miles that stalls in hot weather (>= 90 degrees) when fully warmed up and during a right turn (as well as in hotter weather when coming to a stop and then trying to accelerate).  I replaced the coolant temp sensor as you suggested, and it kept happening.  I then replaced the crankshaft sensor and it kept happening.  I then replaced the camshaft sensor and it kept happening.  I also replaced the MAP sensor and it kept happening.  From time to time, the service engine light would turn on and I would check for codes, but it always has said “no codes”.  

Finally, I started hooking up the code reader even though I had not gotten a service engine soon light warning and I started getting codes every so often!  First I got P0305, which I believe is cylinder #5 misfire detected.   I have most frequently gotten P0171, usually by itself, which is “a lean air/fuel mixture has been indicated by an abnormally rich correction factor”.  I also have gotten a couple times P0300 (multiple misfire) along with P0302, P0303, P0305 & P0306 (#2, #3, #5 & #6 cylinder misfire) or some lesser combination, and one of these times the aforementioned P0171 joined them.  All of these I have only gotten when the service engine soon light has not illuminated.  Whenever it has illuminated, no codes are present.

In the past month and a half the stalling has been happening regardless of ambient temperature, so whatever it is, it’s now failing much more frequently.  The car will stall when it’s 60 degrees outside, and it now doesn’t seem to need to be fully warmed up before the stalling starts.  It still happens mainly on right turns and coming to a stop, but now it also happens in uphill traveling, left turns sometimes and occasional bumps in the road.  And when I say “stall”, what I mean is that the car completely looses power and acts like it’s misfiring for anywhere from 5 to 20 seconds.  When this happens, I lay off the throttle and you can see the tachometer jump around below normal idle (600 – 1000 RPM) as the engine struggles to keep turning.  After the stumbling ends after the 5-20 seconds (depending on how tight/fast a turn), the idle returns to normal and the car drives fine until the next right turn/stop/left/or bump.  If I stay on the throttle, the engine fully struggles and seems to misfire over and over.

Because of the high frequency of the P0171 code, I started thinking that it might be the oxygen sensors, so I’ve just replaced them one at a time, and it’s still stalling.  I am now thinking that this is all about fuel delivery, but the codes I’m getting don’t seem to implicate the fuel injectors.  

Of note, in the past the fuel level sending unit had been malfunctioning in which it would read that the tank was empty and set off the low fuel warning light frequently, despite the tank having plenty of gas.  This hasn’t really happened in the past 2-3 months, but it used to malfunction several times and set off the warning chime during a short drive.  I don’t know whether this is relevant, but I thought I should include it.

Does any of this help to shed light on this baffling problem?  What should I try next?  

Thanks for your continued help,
Paul  

Answer
Hi Paul,
I reviewed the previous question and response. I'm sorry to learn of you continuing problem. It appears to me that there is not a single sensor or monitored component that would be responsible. Rather I would look at the more classical parts. The manual for troubleshooting a 3.8L '96 engine gives the following items to evaluate:
ignition coil
PCM
engine parts out of tolerance
exhaust manifold and pipe (check for leaks)
fuel pump (check psi)
fuel filter
ignition wires
injcectors
MAP
upstream O2 sensor
fuel pressure regulator
fuel pump relay
spark plugs
wiring harness/connectors
I realize that you have replaced several of these.
The testing of the engine using a DRB is focussed toward an exhaust leak between the manifold and the uptream O2 sensor and corroborating the trouble codes are correctly reflecting the operating parameters that would set them.
You might in addition to the list of items above want to check the possibility that your catalytic converter is partially plugged. I believe an exhaust shop can do that quickly and inexpensively.
A fuel pressure measurement would cerainly seem relevant.
So those are my best suggestions.
Please let me know of any progress.
Roland