Howdy! 2000 S40T, runs well but falters when idleing in park and only when no accesories are on ie/ idleing with AC off it falters at around 800rpm turn on AC no falter, Idle in park it falters, put it in gear, no falter...whats up?

 

I run with same problems, except i now idle around 590RPM, check your coils and spark plugs, then battery, then leaks in hoses, sadly there can be about 50 reasons for this.