My 98 V70 has had regular maintenance performed, oil changed every 3500 miles and runs perfectly, except for a "cough" or hesitation it has developed during idle and regular speed driving. The "cough" is almost like the motor tries to die, but does not, and it happens every now and then. It doesn't matter if I am at a signal light or driving down the road. There are no fault codes showing and I am at a loss. Any thoughts? Thanks.