Chrysler Repair: 94 LeBaron will not start after running, controller notes, active controls

Question
Hi Roland,
My dad bought a 94 LeBaron Sedan recently. It is a V6 automatic. It's been running great but the heat didn't work. He installed a thermostat since there wasn't one at all. Ever since he did this if you try to restart the car too soon, after running, it won't start or it starts, shakes violently, and stalls out. It seems like it's flooding and if you let it rest for 15 mins or so it starts and runs fine again. The heat works fine on the car now and the car isn't overheating-the heat range pretty much stays in the middle on the gauge for the engine. Neither of us is sure of any relationship between the problem and my dad installing the thermostat but this is the only "significant" change he has made at all to the car. Any help you can offer will be greatly appreciated. Thanks, Jonathan.  

Answer
Hi Jonathan,
It is probably something related to the mixture as your observed. Most of the sensors and many of the active controls items are monitored by the engine controller. The controller notes malperformance and stores it as a coded two digit number. You can find out what fault codes have been recorded and stored by using the ignition switch as follows: turn key on-off-on-off-on within an elapsed time of 5 seconds or less and leave it in the on position. Then watch for the "check engine" light to begin to flash, pause, flash. pause, etc. Count the number of flashes before each pause and record the numbers as they appear. Repeat the process to verify you have them correctly. Then take them two at a time to form two digit numbers. You'll find that the last set of flashes are 5 in each, which form the number "55" which is the code for "end of readout". The relevant numbers are of course the earlier ones. So let me know what you get and we'll interpret and give you some suggestions on why the engine is misbehaving. It is good to have the thermostat in place as the engine needs it to run economically and cleanly.
Roland