1990 Plymouth Acclaim Won't stay running

Welcome to the forum, how long since a tune-up? Spark plugs--wires-- all filters-- fuel pressure ok? Check for codes. You should be able to get some mil codes by cycling the ignition switch. You turn the key just till the dash lites come on, no further, cycle the key, on--off, on--off, on, then the check engine lite starts flashing, you count the flashes to get the codes. Your looking for two digit codes.