Chrysler Repair: 90 dodge spirit:dies after about half hour

Question
Our 1990 dodge spirit runs for about a half hour then the check engine and check gauges lights appear before it begins running rough and stopped running. We have replaced the alternator, battery, fuses, thermostat. What could be causing this.

Answer
Hi James,
Use the ignition switch to get a fault code that may explain what is wrong. Turn the key: "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 of flashes before each pause. Then repeat the process to be sure of an accurate set off flash counts. Tell me the counts in order of appearance and we'll go from there. Mention which size (L) engine you have.
Please read the PS (below) and respond to it.
Thanks,
Roland