Lol well my step fathers 98 neon is throwing code 31 the only problem is there is no such code in a 98 neon only 95s can throw that code now i have checked it time after time and he gets 12 31 and 55. and his check engine light is always on. the car under acelration from idle will spudder as if its being choked out slightly could this be his tps or his map or the iat sensor

98's can have a code 31...why would they not be able to? Anyway, a code 31 can be any of these problems:

31 An open or shorted condition detected in the duty cycle purge solenoid circuit.
31 An open or shorted condition detected in the evaporative leak detection pump solenoid circuit.
31 Evaporative leak detection pump mechanical malfunction.
31 Small leak detected by the leak detection monitor.
31 Leak detection monitor unable to pressurize evaporative system. Indicates large leak.

I would try reseating all the hoses and electrical connectors and the gas cap, pull the fuel pump fuse for 10 minutes and see if it comes back. If it does then you need to get the P code to tell you exactly what it is.

ehhh i looked at at the trouble codes section in my chilton

and there wasnt a code 31 listed there was only a 31 listed for my 95

ehhh i looked at at the trouble codes section in my chilton

and there wasnt a code 31 listed there was only a 31 listed for my 95Well the Hayne's or Chilton manuals both have some wrong info in them.

Tell your Dad to make sure the gas cap is on correctly. They can throw the code if not seated properly.