Chrysler Repair: Cold Start Problem on 1988 Voyager, coolant temperature sensor, mitsubishi engine

Question
Hi Roland,
You had an opening so here goes.  This is in regards to a 1988 minivan with a 3.0L Mitsubishi engine.  For the last couple years it starts and runs fine during warm weather.  When the temp gets below about 45degrees, it will not start at all, will not fire any cylinders.  If you try to start it near its lower limit it will start and will run if the rpm is kept above ~2500rpm.  If rpm drops below this limit it cuts out, dead.  If it runs long enough to warm up its ok.  
Its pretty bizarre seems to have elements of both electrical and fuel problems.
Any suggestions?
thanks tom

Answer
Hi Tom,
The only sensor that can tell the engine that it is cold weather is the coolant temperature sensor which is located between the thermostat housing (large water manifold with large radiator hose) and the distributor. If you disconnect the two-wire plug by gently lifting the retaining tab you will get access to its two pins that are essentially the two ends of a temperature sensitive resistor. The resistance should be 7,000 to 13,000 ohms at 70F and goes higher than that as the engine gets colder. So if it read less than 7,000 ohm in the summertime morning when the engine is at ambient, then in all likelihood it will be below the resistance that it needs to be when the engine is colder than that. It is a simple screw off/screw-in replacement if it is reading off value.
The other thing to do is ask the controller if it has observed any other faults in the system. The most useful thing to do would be to try to get the fault codes that may stored in the engine controller memory to readout. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the 3.0L and we can look up the possibilities of what is wrong based upon what fault codes you show. The coolant temp sensor fault code is 22 but if the resistance is just slightly off value it might not trip the code threshold.
So let me know what you find.
Roland