Chrysler Repair: 91 3.3L warm stalling


Question
QUESTION: My 91 Chrysler New Yorker stalls, kicks, sputters, etc. only in the mid warm range.  It starts cold just fine and runs excellently until it gets partially warm, then it runs terrible until it gets fully heated and then all is well for the rest of the day until you turn it off and let it cool down for a couple of hours.  Then the sequence starts again.

I'd hate to junk this great car for only 5 minutes of lousy running.  I call it the "2nd mile syndrome" as it is only during that approximate 2nd mile of running.

Most sensors, the coil pack, thermostat, spark plugs & wires, fuel filter, computer brain, etc. have been replaced in trying to solve this over the last 3 years.

2 Chrysler dealers and my long time mechanic and other "online Chrysler experts" cannot solve it.

ANSWER: Hi George,
Did you do a fault code readout using the ignition switch? Turn it "on-off-on-off-on and leave on", doing that in 5 seconds or less elapsed time. Then watch the check engine light which remains 'on' to see it begin to flash, pause, flash, etc. Count the number or flashes before each pause. Then repeat the process to be sure of an accurate set of flash counts. Let me know counts in the order of appearance.
If there is nothing other than two groups of 5 flashes each, which means 'end of readout', then the only other part I know that isn't well-monitored is the exhaust gas recirculation valve (egr). That might be hanging up ajar which then unpredictably causes a poor mixture. Locate the valve and then put some WD-40 on the valve stem where it enter the body of the valve,  and work it back and forth by means of a screwdriver tip inserted in the slot of the valve stem. Let me know which engine you have and I can tell you how to find it if you don't know where it is and also I can describe the valve.
Please read the PS below and respond to it.
Thanks,
Roland

---------- FOLLOW-UP ----------

QUESTION: The engine is a 3.3L V6.

Yes, I have checked the Fault Codes.  They are presently reading:
12 - 62 - 55
Which may or may not tell us anything serious.
12 simply reflects the battery/computer recently disconnected
62 means PCM failure SRI mile not stored (the odometer is not working and could this mean that the PC can't read it?)
55 = "the end"

I don't believe anything has been done with the EGR.  

The car is presently in another Chrysler dealer shop and I don't expect it back for a week.  One of the reasons I will never deal with a Chrysler dealer.  I will check the EGR then.

Failing that I might try a new computer or junk the car.  This problem has drug on far too long!

Thanks

Answer
Hi George,
The 62 code probably is due to the discrepancy between the mileage reading recorded in the pcm and in the instrument cluster. I would doubt this is related to the rough running.
So check out the egr valve when you get the car back. It is located on the firewall side of the engine, under the throttle body. It is mounted at the end of a narrow pipe that branches off the exhaust manifold midline on that same side. It is mounted sideways and has a vacuum-operated round top, and between the body of the valve which is attached to the pipe you will see a flange inside of which is the horizontal valve stem with its slot. So spray some WD-40 on the stem where it enters the valve body, then 'exercise' the valve back and forth, noting spring-action which tries to shut the valve. Make sure that does move to a dead stop under spring-action. Then see if that resolves the problem.
If not, then I would believe that one of the sensors is probably inaccurate, but not so badkly as to set a fault code. I would believe that a tune-up mechanic with a Diagnostic Readout Box that shows the 'live' operating parameters of the sensors would spot which one is faulty. Because it is related to temperature it might be either the charge temp sensor or the engine coolant temp sensor.
If you would do the rating and nomination I would be most appreciative.
Roland