My brother has a 1990 firebird with the 3.1 liter and its running really rough has no power and when he starts it up it revs at around 2000 ta 2500 rpm then goes back down below 1000 rpm then eventually stalls not too long after could that mean his distributor could be bad? And also before that happened his car would not start at all then he changed the spark plugs then it started but started doing what I explained at the top.