my engine when idling makes popping noises out of the tail pipe....i have a d16a6.....and when i am in 5th gaer going 35-40 mph it will backfire when i mash the gas down....could it be a piston misfiring, or bad spark plugs?help..

 

maybe its time for a tune up.... my ---- was starting to do that poping noise at idle... I got new plugs, cap, rotor, and set the timing back to stock settings... reset the ECU... and it runs good again.. no poping noise or unwanted surges...

1 more thing.... going 35-40mph on 5th gear is not the smartest thing to do...3rd gear possibly 4th at the most for those speeds